I didn't catch exactly how old these girls are-oh wait-14 yikes!!! I would have a very frank, positive, loving conversation about your fears, which to me would be safety. And you do have the right to some authority. Her little friend does not know about all the diseases passed orally as well as vaginally, and she certainly doesn't care that she's getting an EARLY start to all the disease catching she'll be doing. Like all girls acting this way, she's seeking attention, excitement, and approval from boys. She likes bragging. She doesn't get it that the guys don't really "like" her for it.
Your daughter is a little bit impressionable (and only 14 for heaven's sakes) if she got drunk with the girl and likes her so much etc. That would be the last time my 14 year old was ever at her house. You should encourage her to tell her friend she can get herpes and warts and pretty much any STD by orally servicing guys who love to "put in anywhere" because i'm sure the friend just feels talented for knowing how to do it. Not trying to sound mad, but really, this girl hasn't had good guidance. Give your daughter some news to tell HER for once.
BUT, I think you're right to have confidence in your daughter and keep open. If you have taught her right, (sounds like you have which is why she talks to you) she won't necessarily copy her friend. Several of my best friends were slutty in high school (more like 16, 17 though..) and I was a big prude. But nowadays, the kids are starting so young, and it's so widespread it's harder for girls like your daughter to stand firm for so many years.
Don't do anything rash, but spell out what disturbs you about this girl and how your daughter seems to prefer her. Don't lay down any laws (actually I would though), but let her know how you feel about her choice to spend most of her time with this friend and how you'd LOVE it if she made some different ones, and make sure she knows the dangers involved with the casual sex attitude. Do it in a "Kids are so funny, because sex matters so much to them. Oldies like me have seen and heard it all before and I can't believe she's putting herself at risk like that so young...guys don't like that type, they just use them in high school.....I would be devastated to think you might get loose and uninhibited with her and end up hurting yourself." That's all you can say really. But at 14, you should put down your foot still on hangin gout with that friend. It doesn't have to compromise your relationshi if you're coming from a place of love. I feel for you and in about 10 yearsI'll be in the same boat with 2 daughters...noooooooooo!
Oh, on the side, idle hands are the devil's playthings. Good thing you have close tabs on her time. Depending on her age, it's time to keep her busy with activities to prep her for college, a part time job, a church group of kids wouldn't hurt, etc...Not only was I not allowed to "hang out" with dudes and party girls, I didn't have time in high school I was working so much. Sure, I managed a few social outings where people my parents didn't approve of were around, but not all the endless hanging out I see kids doing a lot. Keep her busy and away from that friend!