Stealing is taking what is not yours. You gotta see who name is on the account so if her name is also in it as a joint account then she can extract it so no, it is not stealing.
Now did she make the right decision, that is subjective. Had that was me, I'll biatch and moan about it for a bit but she'll end up knowing my trait and know that i'll get over it and close the case by the following day. I'll go make more money, no big deal. Women, if you love them, they'll do things that will drive you nuts and get away with them small time crimes.