Is he playing my sister?

My sister is in an LDR.

Her boyfriend is at University on placement. For the past two weeks, two days a week(so four times total so far), he'll tell her he has to go out to dinner with people from his placement.

He says they're the people who operate the placement along with other staff members but he stays out until 1-2am. She asks why 50-60 year old women are out until 2 am with him as well as asks him if any other students are there. He says a few but he doesn't know them because they're not the ones who work with him so he mostly just spends his time talking to the nonstudents.

She told him she finds this weird that he does this twice a week, he says it's for a fundraiser but doesn't go into detail. He has done fundraisers with them before but this sounds weird. She said he told her that they just discuss fundraising and stuff.

This is TMI but my sister told me that he doesn't flirt with her on Skype as much/"talk dirty to her" these past two weeks.

IIN? Is she getting played? The rest of the week, he is home before then and isn't at a pub.