I'm thinking the guy is the one who needs to run.

Guy is a nice guy who probably has hard time telling someone no. He was probably contacted by this girl, who said whatever the scandalous girl needed to, and he just doesn't have it in him to be rude and not respond. His personality is used against him and he ultimately helps this girl out. He doesn't really want to do it...but he just doesn't have it in him to ultimately say no. He justifies it by thinking he did a good deed.

He knows he can't tell his significant other when it's happening because he knows she, like the majority of women in general, will almost certainly create a fury of unnecessary drama that he honestly just doesn't want to deal with. Afterall, he already feels like a schmuck for not standing his ground loaning money.

The last thing he wants to add to this deal is a crazy, untrusting, jealous women who will no doubt turn this bad scenario into a long term nightmare. She is not mentally mature enough to handle this scenario. She has a bad history with previous men and he has obviously started to pay the price.

He is no longer his own man and is slowly and steadily transitioning from living his life to just existing in hers.

As time passes, his clearly correct decision to not tell her fades and the sting of being ripped off strengthens. He mistakingly believes he can now tell his significant other and enlist her help. Afterall, he didn't do anything wrong. This scandalous girl will have no choice but to respond to her friend.

And now....reality just hit him like ton of bricks. Still ripped off and still just existing in life with a jealous, untrusting control freak.