She IS using you, she's an active addict and there is no such thing as a healthy relationship with an active addict. I am sorry you feel hurt but I promise you that if you remain connected to this person, you will lose a lot more than you have already. By giving her money you are buying her drugs, and that's always a reason for them to stick around.
From your story, I suspect you are with her when drug deals are going down...and that, my friend, could land YOU in jail.
You are lonely, I understand that, but if you want healthy friends you have to be healthy too. Healthy attracts healthy, sick attracts sick.
Maybe find a meeting for co-dependents, Al-Anon, CoDa or Nar-anon...or since you say you struggle with alcohol, AA may be just the place to make friends and learn to live a healthier life.
This will end when you say this ends, you are the only person who can pull yourself away and find a better path. I pray you do that soon, before it gets worse.
“Hello, sun in my face. Hello you who made the morning and spread it over the fields...Watch, now, how I start the day in happiness, in kindness.”