Gosh this sounds very hard indeed op 
Although we are through the worst now at 18 yrs, I recognise some of the behaviour you describe but in a milder form. My dd and her friends don't really drink a lot or do drugs and have been fairly good with their studies, and they come back home at a reasonable hour after going out, so I think we have been fairly lucky from a peer pressure point of view.
The things that are similar though have been the "flick of a switch" aspect of the personality change which we put down to hormones. Also, our dd has had quite a lot of stresses at school and the pandemic has been really crap for all youth, and that has caused a lot of frustration I think which gets directed at us her parents mainly me.
I am probably going to be flamed saying this but I also suspect, judging what I see among dd and her friends , that there are a lot of unhelpful influences on-line which do not exactly encourage family harmony eg there seems to be an attitude of teenagers feeling very hard done by even when they come from good, loving homes and have parents who, while not perfect in many ways, want the best for their dc and are concerned for them and love them. That is pure speculation on my part though.
Also, there are the physical and biochemical changes eg plasticity of the brain which are as profound as those undergone by toddlers Teens simply do not perceive the world in the same way as adults do, not until their frontal cortexes develop at 25 yrs approx anyway.
My advice is to step back. Protect your own mh. Be there in the background for emergencies and keep lines of communication going and only step in if there is a life threatening situation. The rest of the time, do not offer unsolicited advice, just try and guide with the lightest of touches. Involve yourself in your own interests. Model sensible, measured, behaviour and enjoy interests of your own. Do things which keep you buoyed up mentally. Keep supplying your dd with nutritious food and encouragement. And let her get on with her life until things get better, which they WILL do!
Hang in there op
The fact that things were better before the summer is a good sign. Teen progress is rarely linear!
Btw, I would be very wary of getting too heavily involved in university choices. You can advise but don't push too heavily in either direction. Hard though it will be if she chooses to opt for a uni close to home, it needs to be her choice. Otherwise you will get it in the neck for having influenced her the wrong way and she then has an excuse to self sabotage. Going to uni at home doesn't necessarily mean not moving out to separate accommodation after the first year, and with the pandemic ongoing. terms can be very short anyway and holidays long, so it may not be as big a break as you were anticipating if she goes to uni further away. Also its very damaging to your relationship if, despite everything, she gets the impression she isn't loved or wanted at home.
I think it is in the book "Untangled' by Lisa Damour, where the author explains that those teens most 'entangled and entwined and close' (or words to that effect) to their parents, are those who find it most hard to pull away and individuate from them.
And although it appears that your dd is doing quite a good job of it
inside she may be full of self doubt and turmoil.
It's hell while it is all going on though so I really feel for you 