As a male, this is not a problem I ever had, but I believe her. She isn't making it up.
Grow up.
If she were interested in bedding the most attractive males possible, then maybe. But what she actually wants is to build cool environmentally efficient buildings, and to do that she needs to pass her classes.
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.
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.
That your daughter is rejecting them outright would suggest that it's either a futile plan anyway, or that the women are already on to it so the announcement would be pointless.
Perhaps your daughter doesn't need or want to cash in on her attractiveness for academic favours. Others will, quite readily. Men sure as hell aren't saints, but nor are women.
Some people are just nice, some are looking to make friends, some may be confident about certain aspects of the course & want a support group for the parts they are weaker with, and some are just passionate about a given subject so they offer to help or study with classmates.
Unless the person is being super obvious, it's pretty hard to to tell whether the person offering help is one of the above types or if they are just trying to get in your pants until after the fact. When I was in uni, this was a constant issue among my female friends and it constantly left them on guard.
Then when the guy would make their intentions clear and inevitably get rejected, it'd be a coin toss whether they'd respond negatively as if they were owed for their assistance. It's mentally exhausting relying on people, having to constantly second guess whether they might want to sleep with you, and how to handle things in the event they try. Worst case if you are isolated (in a dorm, empty classroom, library study cubicle, etc), they might try to "take what they are owed" or make threats for "deceiving them". More likely they'll just drop any effort put towards helping you as you are now a missed mark and mid semester you'll have to quickly try to find someone else to study with or work on assignments with lest you fall behind.
Of course not all cases end badly but enough of them do that the majority of women will have at least one experience with some degree of retaliation for rejecting advances.
This of course is only worsened by male students like in the post who are auditing the class (i.e. no penalty for failing or stopping participating) with the explicit intention of trying to sleep with other students in the class. With the case in the post, there is even less of a chance of those making advances simply accepting the rejection and continuing to work with you. Also this particular case could be additionally problematic because if it's as pronounced as the post describes, it might shift the grade distribution (and therefore the end-of-course curve) which sets bad incentives for students.
And yet the complainants are complaining about not getting attention, which seems like a different problem that your daughter is experiencing.
Young women aren't oblivious to their own charms. They know what they're doing. They're getting free 1-on-1 tuition from a nerd, and the nerd gets to be within 3 feet of an attractive young woman - maybe even more than that, let's not be naive about college campuses - which might otherwise be impossible. Everybody wins.
You might even upset the women most of all! When the quiet part is said aloud, you take away their plausible deniability. You're calling them out even more so than you are the men.