Hershey's, welcome to SoberRecovery.
Something that jumped out at me was that she had been sober for 2 years...is that what she said or are you certain of this? It just seems odd that she would relapse within such a short time of being with you (and she may have used before this but didn't get caught).
My son used to tell old girlfriends that he had been clean 5 months or a year or whatever fit the time that they didn't know where he was. He hadn't been clean 5 hours when he told the 5 month lie.
It's up to you whether to continue this relationship or not, but I just don't see what's in it for you. A lifetime of riding the addiction roller coaster can wear us out pretty fast, and sadly that's often the case. Some get clean and stay clean, but your girlfriend doesn't sound anywhere near ready yet. And sadly nothing you do can make her be ready.
If love could save our addicts, not one of us would be here.
Also, you have two children to think of. Growing up in a home with addiction, not to mention the danger of drugs that might be hidden at home, can do them harm for the rest of their lives. Is this what you want for them?
Please know that as harsh as this may sound, I am saying it all with compassion for her and for you. I know the pain of watching someone we love destroy themselves, my son is an addict.
Take a read around and make yourself comfortable. I'm glad you joined us and hope you find support here that helps you.
Hugs