Tricky... she didn't say anything, just rocked up as if nothing had happened? Wow.
If you can, stay calm as anger can come across as aggressive and scary. But do say something as otherwise it will be gnaw away at you. I am not a fan of confrontation myself but my advice would be to stick to the facts and how you're feeling about things - no finger pointing etc. Best not to ask where she has been etc otherwise it turns into an interrogation and no one likes that
If she has identified that your drinking is a problem, do listen to what she has to say - we often like to jump in and get defensive when someone points out our weaknesses as it hurts. But that honesty shows that she cares and wants to move forward. I can't know what is going on with her, but I hope you get to talk things through. You have both been through a lot, but the pressure can get too much.
Final thought - have you spoken to your GP or anyone about how you feel? Having to be the sensible one, the together one, takes its toll. GPs are there to help us so I'd recommend you make an appt for a chat.
Good luck and sending hugs