If she was drunk then sex = rape.
Rape = sex without reasonable belief in meaningful consent.
Meaningful consent cannot be given if participants are drunk.
WannaBe, men are the ones who by definition rape in UK law. It doesn't matter if he was drunk too because he is the one with the penis. Without consent, sex is rape, and rape is committed by men, under UK law. Rape victims can be male or female as rapists can penetrate either males or females.
If the male is too drunk to distinguish consent from lack of consent then sex he engages in may well be rape as he would have no 'reasonable belief' in consent, being too drunk to form an accurate opinion of the other party's response. If he was not too drunk to form an opinion, then he might also have raped, depending on how drunk the girl was.
There are details that indicate that this girl did something out of character with this boy. She has had sex with boyfriends she has been dating in the past but not with individual boys on a FWB basis. She has in the past kissed this boy but not gone further and there might have been reasons for that including not wanting to have sex with him. No protection was used when she and this boy had sex, and she needed to use MAP and hopefully will go and be tested for STDs (hopefully negative, OP) She now feels confused about what happens next, in terms of the relationship with this boy.
These details point to a lack of intent to have sex with this particular boy that night, and the fact that they had both been drinking leads me to ask about consent.