But honestly, stealing $120 of what is suppose to be a gift to someone else? Can people really behave that way and think they can get away with it?
Yup. At a past employer, it was common for us to pass a card and a brown envelope around the room. Sign the card, stick the few bucks you had leftover from lunch in the envelope, or more if you felt like it. The envelope usually got the person being honored a nice gift as we were a 24/7 shop. We had one occasion where we (dayshift) left nightshift the brown envelope & card. The money was left in the envelope as there had never been a problem with it before. We came in the next morning and the money was gone. [I'm fuzzy on the details. I can't remember if the whole thing was missing or just the cash.]
The pool of possible thieves was limited, as we worked in a room accessible only by us (ops staff). But management was not able to figure out who had done it. The last time it was seen it had all of the money in it.
There were, however, suspicions. And those suspicions were laid at the feet of one of the night shift employees who had been living beyond his means. The money disappearing came at the same time as Diners Club informed our employer of the employee's maxed out delinquent account.
Money collection methods changed after that.
OP, I don't believe your DD should quit the committee. I think it is a very bad idea to do so right now and would only look suspicious. I wouldn't go to work with anything brand new for awhile either.