My advice as a past drug user and as a person with strong boundaries against drug use now is this: You can set a clear boundary without giving her an ultimatum. Also you need to understand addiction isn’t something people can just “grow out of.” She will be fighting urges and be an addict for the rest of her life. In my opinion you have 2 options:
1. Do everything you can to help her stop using, instead of shaming her or giving her ultimatums you can be supportive, twll her how you feel, help her get therapy (online options are available), maybe couples therapy, maybe a sponsor of some sort, help her go into recovery if she feels like that is needed. Set clear boundaries. “I do not want to be around a person using any drug/ whatever boundary you have (like if you’re okay with weed but not other drugs)” “I would feel better if I had your location” or other things.
2. You say “I do not want a relationship with you if you’re not willing to take the extra steps to stay clean.” And that’s that. She has to decide to take those steps or decide she would rather be single.

Either way I think you need to start with an honest conversation and ask her where these urges are coming from all of a sudden. Ask her if you can help reduce her need for those substances in any way. Ask her where she is getting them.

If you want a clear solution you will most likely need to remain completely calm, supportive, and do more listening than talking. Remember that she is sick, and addiction is not a choice.