I think a number of posters have been too dismissive of the OP's concerns, especially about the pot issue. Many people here are pot positive so that is understandable.
However, there is also the case of Henry Granju whose mother, Katie Allison Granju, is a name in attachment parenting and who died of an overdose after being involved in both dealing and prostitution for drugs. He started with pot, and Katie has written on her blog that she wishes that she had taken that first discovery of his pot usage much more seriously.
I think the OP's mom should reach out for help (perhaps from a therapist or other substance abuse expert) to get better strategies on moving forward with her relationship with her daughter and addressing the various issues raised by her behavior.
Pot usage in college is not restricted to the hippie, crunchy type -- in fact, at my college, most pot smokers were actually frat boys. I would have serious concerns about a relationship between a high school sophmore and a college guy due to the power and experience differential. He could be a good guy but I would suggest that what we know about his behavior so far indicates otherwise. He may be more the type who, back in my day, liked to call the incoming freshwomen "fresh meat."
However, I think that the ship has sailed on the virginity thing. I would be managing that with discussions about safe sex.
The drug usage issue is much more serious and that would be my focus going forward.