I (m22) caught my girlfriend (f23) in a massive lie.

I (M22) found out my girlfriend (F23) has been lying to me for months. About 6 months ago my girlfriend started becoming extremely depressed and stressed out and told me it’s because of post partum depression from her pregnancy. Because of this she’s been working less which means I have to work full time to cover all our bills on top of going to college full time as well. It’s been hard to get through these last 6 months and even with me working full time we’ve been struggling financially. I talked to her several times over this period telling her that I feel like something’s off and I could almost say for sure she was hiding something from me, but every time she’d just blame it on the depression and yell at me for falsely accusing her. Fast forward to last night when one of her friends from work decided to send me screenshots of my girlfriend and her other coworkers talking about doing coke in the bathroom at work (which is something we’d promised each other we’d stop doing when she got pregnant with our daughter). I was shocked when I saw this and decided to go through her phone while she was asleep so I could confirm weather or not it was true. Sure enough I found tons of evidence that her and her friends had started doing it about 6 months ago which is exactly when her entire attitude changed. It only got worse when I looked at her payment history and saw that she’s been sending $300 a week to her dealer while I’ve been struggling to pay her bills and buy her the things she needs. I felt extremely hurt by the fact that she could keep something like this hidden from me and spent the rest of the night sitting in the living room. Once she woke up she came out to look for me since I wasn’t in bed and I confronted her immediately. She denied it at first but once I mentioned I had already seen the conversations she broke down in tears. She told me everyone at her work does it and they pushed it on her, but she really can’t blame anyone else for letting it get this out of hand. She gave me all the coke that she had been hiding from me( which I immediately threw out) and also agreed to find a new job on top of completely stopping communication with everyone involved. I’ve agreed to not tell anyone we know about her drug problem(mostly because i don’t want them seeing the mother of my child that way). I could tell that our relationship is more important to her than than the coke and her friends, but I just don’t feel like I can trust her anymore. We’ve been together almost 3 years and I still love her a lot, I just don’t know what to do now.

Update: I really wanna thank everyone who commented to help me out with this situation. I first made the post right after I had found out about all this and I’ve had a lot of time to gather my thoughts and find out more about what was really going on. Many of you seem to be concerned about whether or not she was breastfeeding, I realized I probably should have mentioned that our daughter has been on formula since birth so she hasn’t been exposed to any of this. After my last post I had her quit her job immediately and put her in contact with a girl I went to high school with so she could get out of that environment as fast as possible. I also made sure she blocked everyone involved on every platform to keep anyone who might be a poor influence away from her. I signed into to all her social media on my phone and had her texts linked to mine without her knowing so she thinks I’m done looking through her stuff and I can see if she tries anything sneaky. The shock of everything has worn off since my last post and I’ve just been left with the feeling of complete disgust. I did find out that some of her other coworkers would give her cash and then she would cash app the plug for all of them, so she wasn’t spending or doing as much as I had originally thought, but the massive breach in trust isn’t something I think our relationship will be able to recover from. As of right now she has passed drug tests and hasn’t shown any signs of withdrawal. I really just want to thank you all again for the advice.