A lot of this is none of your damned business.
This girl is simply using the resources of the University to her best advantage. Which I imagine you or anyone else would, if you could. Do your professors believe her? Well, they aren't professors for nothing. They might actually, you know, have brains. If you have concrete proof of cheating and plagiarism, then of course bring to the professors' (and dean's) attention. If not, then it's just rumors.
As for her friendship with this man, who the hell cares? Are you jealous? Are you interested in her? If not, then butt out. And, hell, even if you are, butt out. People are allowed to have relationships, yanno.
As for her trying to take your "jobs", that's pretty amusing, seeing as she most likely can't hold down more than one job at a time. I think you mean that she's trying to get you all fired. Well, talk to your boss, not us! And have documentation. Again, you need proof - otherwise it's just nasty rumors. Perhaps this girl is innocent.
As for her being cheap, again, none of your damned business. If your friend wants to pick her up, then he'll do so. If not, he won't. If he wants to invite her, he will. If not, he won't. I fail to see where you are involved in any of that nonsense. As for her asking for a ride, well, you have no idea whatsoever of her life, now, do ya? Maybe she's poor. Maybe she has bad night vision and can't drive. Maybe she's a mutant zombie looking to eat the brains of your friend.
So much drama, so little of the business is your own. Are you this bored and unchallenged in your life that you need to gossip about this woman anonymously online?