Jason, I'm in no position to give any LEGAL advice, but I can possibly give you a creative solution so you can avoid needing legal advice. If you happen to have a vacant property that
A) she can afford and
B) would be interested in the location
you could offer to credit her half of the security deposit towards her new security deposit. She's going to have to live somewhere, and unless she's bumming a couch somewhere, the new place is going to require a security deposit. In fact that's probably part of the reason she wants the cash. I'd run this by her, and see if you can help her solve one problem she's facing during this extremely difficult time in her life.
Depending on what kind of tenant they've been, and how much the original security deposit was, you might consider just letting her have the money, no questions asked. I don't know their situation, but divorce is one of the worst times in a persons financial lives. Even more so for many women who have spent many years focusing less on their own income potential and more on providing non-monetary things for her family.
If you can afford it, and feel it might be the right thing to do, it would be very kind of you to help this lady out by allowing her some slack on what is likely to be only a couple hundred bucks. Even if she's not interested in renting from you now, she may need a place in the future, and think of you. Also consider the word of mouth advertising she might provide you.
Either way, best of luck.