The money you withdrawal early from 401K is considered income and will cause you to have to pay taxes.

In your example, if you withdrawal $30,000, you will be in the 15% tax bracket. (This will give her $30,000 of income.)  After taking the personal exemption, you will probably wind up owing about $4,000 in taxes, plus if you are under 59 1/2 you will also owe a 10% penalty for early withdrawal.

There is not capital gain tax on withdrawals from a 401K.  Everything is calculated as ordinary income and subject to income tax. So to make the calculation, you just calculate the amount of the distribution as income and then calculate what bracket she would be in to determine the tax. Here is the table to calculate the tax. http://www.moneychimp.com/features/tax_brackets.htm

You can not make withdrawals from a 401K unless they are financial withdrawals or non-financial hardship withdrawals.
There are two kinds of hardship withdrawals. Financial and non-financial.

To make a withdrawal from the 401k,  you have to qualify for a hardship withdrawal and your plan has to allow one.  Some plans do not allow a hardship withdrawal. A hardship withdrawal may be made from a 401(k) only if the distributions is made on the account of an immediate and heavy financial need and the distribution is necessary to satisfy the financial need. 

The determination of whether you have an immediate and heavy financial need is whether you have other resources reasonably available to the meet the need based on your specific situation.

The distribution will not be treated as necessary to satisfy an immediate and heavy financial need if it can be satisfied from other resources that are reasonably available. So what you have to do is make a written representation that the need can not be relieved by:

1. Reimbursement of compensation by insurance or otherwise.
2. By reasonable liquidation of your assets.
3. By stopping elective contributions
4. By other distributions or nontaxable loans from any other plans.
5. By loans from commercial sources.

The regulations state that the distribution will be deemed to be necessary to meet a financial need if you have obtained all other distributions and nontaxable loans currently available under all of your other plans. 

Also, in the above cases, you still owe the 10% penalty for early withdrawal if you are under 59 1/2 and still have to pay income tax on the hardship withdrawal. So you need to do the calculation to see how much you need to withdrawal so you have the amount you need after you pay the taxes, assuming you qualify for the withdrawal.

If the above conditions are met, you can use the money for:

1. A primary home purchase
2. Tuition, room and board and fees for the next twelve months for you, your spouse, your dependents or children (even if they are no longer dependent upon you)
3. To prevent eviction from your home or foreclosure on your primary residence
4. Severe financial hardship
5. Tax-deductible medical expenses that are not reimbursed for you, your spouse or dependents.

There is also something called a non financial hardship withdrawal that avoids the 10% penalty, not the income tax, but you have to meet certain requirements.

They are:
1. You become totally and permanently disabled.
2. Your medical debts exceed 7.5% of you adjusted gross income.
3. A court has ordered you to give money to a divorced spouse, a child or a dependent.
4. You are permanently laid off, terminated, quit, or retire early in the same year you turn 55 or later.
5. You use the amortization, initialization, or minimum distribution tables to take equal payments for 5 years or until you reach 59 1/2, whichever comes last.  So for example if you were 57 you would have to make the withdrawals until you were 62.

You can make distributions from a 401K, but each distribution is subject to 20% withholding. So in you $30,000 example, you would have $6,000 withheld and receive a check for $24,000. (From that you would also owe $3,000 in early withdrawal penalties.)  You would probably get about $2,000 of that back at tax time, but you will still owe about $4,000 in income tax plus $3,000 in early withdrawal penalties.

A better move would be to roll the remainder of the 401K into the existing IRA. Or, make the withdrawals from the IRA first since there is already money in the account. Then roll the other 401K money later. There is no 20% withholding on a direct rollover from a 401K to an IRA. Then she can make withdrawals from the IRA is smaller increments and thus reduce her tax liability. She would still owe the 10% penalty. Plus, withdrawals from an IRA are not subject to the 20% withholding rule.  It is subject the regular income tax withholding rules just like a paycheck from work, unless you choose to waive the withholding.  But in that case be carefule that you do not owe too much tax at the end of the year because there could be interest and penalites for not having enough withheld.

This is the biggest problem with IRA and 401K.  Whether you want to or not, you must start taking money from the plan at age 70 1/2 (suspended for 2009 only because of the recent market meltdown.) These distributions are called Required Minimum Distributions. Here is the table to see what it looks like. http://www.bankrate.com/finance/money-guides/ira-minimum-distributions-table.aspx. So you can have no income one year, and suddenly the next year find youself in the 15% or 25% bracket.  And payments from Social Security are also included in the calculation thus pushing up your tax bracket.

The main thing to remember is no matter when the money was put in the plan or what company hold the money, each distribution is calculated as income and taxed based on her tax bracket.

Wealth Advisor 
 source:askville

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 No Tax on 401k Loan 
Many plans also allow employees to take loans from their 401(k) to be repaid with after-tax funds at pre-defined interest rates. The interest proceeds then become part of the 401(k) balance. The loan itself is not taxable income nor subject to the 10% penalty as long as it is paid back in accordance with section 72(p) of the Internal Revenue Code. This section requires, among other things, that the loan be for a term no longer than 5 years (except for the purchase of a primary residence), that a "reasonable" rate of interest be charged, and that substantially equal payments (with payments made at least every calendar quarter) be made over the life of the loan. Employers, of course, have the option to make their plan's loan provisions more restrictive. When an employee does not make payments in accordance with the plan or IRS regulations, the outstanding loan balance will be declared in "default". A defaulted loan, and possibly accrued interest on the loan balance, becomes a taxable distribution to the employee in the year of default with all the same tax penalties and implications of a withdrawal.

Loans are paid back by post-tax monies, so there are substantial tax implications in taking a loan from pre-tax monies.  
Sources: http://www.womens-finance.com/401k/cashout.shtml