Hustling my besties ex out of $500. Opinions

So one of my friends was briefly in a relationship with someone that she met through me although I didn’t set them up. Things went south after 4 months but they had planned a trip for vday weekend and she paid for the trip with the understanding that he’d pay her his part, even after they were no longer together. Eventually he stopped responding and ghosted her and left her with his part of the trip to pay for. She wasn’t even asking for the total amount. Now he’s saying he did pay 😓 I believe her but anyway this is my question:

He reached out to me to paint a portrait for Valentine’s Day. Apparently he met someone and is in love (I know this cause he’s in my bf’s circle of friends). The only reason I’m considering it is to get money from him one or another and give it to her. He’s saying he’ll pay me whatever I ask for so I’m thinking of asking for the amount he owes her and give it to her. Would you be upset if you were her? She’s a single mom, I want her to her damn money especially because I feel partially responsible she’s she met him through me.