I'm not clear on the income/tax situation: "If she doesn't make enough money from which to deduct IRA contributions."
So let's start with the mechanics. First, as
@Gary1952 said, don't take a taxable distribution. If you're going to pay taxes, you're better off rolling it into a Roth. All its future earnings will be tax free, as opposed to taxable in a taxable account.
The law allows rollover conversions directly from a 403(b) into a Roth IRA. This eliminates one step in the conversion process. But my limited experience in helping someone do this within TIAA suggests that the 403(b) administrators may not know what they're doing. (In that case, TIAA withheld state income taxes which they were not supposed to do.)
Instead, a direct rollover to a T-IRA will preserve your options to convert or not. If you should convert the IRA (or a portion) to a Roth, don't have taxes withheld, else the amount withheld will be treated as a taxable withdrawal. In addition, the conversion money
cannot be withdrawn penalty free for five
years. Because your wife is (and will continue to be) under 59½ the conversion money will be subject to the usual 10% early withdrawal tax until it becomes a qualified distribution. That happens five
years after the conversion.
Here's a short column discussing these two "traps":
https://www.irahelp.com/slottreport/roth-ira-conversion-10-penalty-trapIn some states (I don't remember which state you're in), some retirement distributions (including IRA withdrawals/conversions, pension plans, etc.) can be taken state-tax-free. This feature may be age-restricted. For example,
Colorado exempts $20K of retirement income (including IRA withdrawals) for people aged 55-64, and $24K for seniors. So if you're thinking about converting the money, it might make more sense for you to convert part of your T-IRA (if any) rather than part of your wife's. Not to mention that you're closer to RMDs.
Page with table of how each state treats retirement income:
https://taxna.wolterskluwer.com/whole-ball-of-tax-2018/state-retirement-taxesThat gets us to whether it even makes sense to convert (which is effectively what you're doing if you do a direct rollover to a Roth). Not enough information to reasonably comment here, especially since I don't understand what you mean by "doesn't make enough money". Generally 100% of compensation can be contributed to T-IRAs (up to contribution limits, of course).
The 12% bracket that
@bee mentioned calls to mind another consideration: 0% capital gains. If you keep your total taxable income under $78,750 (sic), then you cap gains are taxed at 0% by the IRS. Note that this limit is slightly different from the $78, 950 limit for the 12% ordinary income tax bracket (MFJ).
Too many considerations and too little information to comment intelligently about your conversion decision (which would be informational in any case and not constitute advice, as with all of this post).