At no point are the men getting mad at her or expressing that. They're not like, "Well fuck you, ya damn stupid cunty bitch." They're not doing that and you know they're not. If she just says no thank you then all they do is walk away feeling down. If instead she's super aggressive and an asshole about it like: "ew no, you fucking incel dweeb. Fucking die!" then maybe they have all the reason to be mad at her.
Doubt your daughter is going to be telling you when she acts like the later though.
She a) doesn't get invited to mixed gender study groups, and b) doesn't get picked for mixed-gender group projects. And no, it isn't because she's not a good engineer or a hard working team member.
Human interactions are complicated and it's hard to say that there is only a single reason for anything anyone does or doesn't do... but having been rejected sexually by the young women in your class doesn't do much for your group dynamics.
I’m not friendly to anyone who acts like an asshole to me.
Your daughter is also probably just not attracted to the overwhelming majority of those men. She’s probably quite picky. Very common with engineering women since they have endless options.