I’m very sorry this relationship has become so disappointing. I think you already know what I’m going to say: Your girlfriend is more committed to her relationship with weed than she is to her relationship with you. Clearly, she is one of the people who can’t handle marijuana and who needs more than good intentions to quit for more than a minute. If she were serious about quitting, she would get herself into counseling or a support group or an addiction program. Instead, she is using emotional blackmail to continue having you in her life while she continues to smoke.
She may say she hates you if you leave her. But leaving her may be exactly what she needs to “get it”. Many people with addictions need to do what’s called “hitting bottom” to wake up to the cost of addiction. Sadly, there are people who need to lose the love and support of people who love them before they are willing to admit they need help. If she is like that, it is doing her no favors for you to keep going back for more heartache.
I think you should lovingly tell her that you can’t be in a relationship with both her and weed. Let her know how much you care and how much you wish it were different. If it’s true, tell her you would be willing to try again after she’s been quit of weed for 6 months but no sooner.
If she says she loves you but can’t do that, she is in serious denial about the hold that weed now has on her. In that case, I hope you will take a big step back from the relationship and make yourself available to other people. You deserve to be the first in someone’s life — not playing second fiddle to weed.
I wish you well.