Hi bolete, you can rest assured you're not the cause of them drinking. No-one can cause another to drink unless they tie them up and force feed them.
You may have a particular type you gravitate towards, or your ladies might have been hiding the true extent of their drinking when you met them and gradually relapsed.
Your partner doesn't sound serious about sobriety. Maybe she isn't convinced she has a problem, but because of your background it's a problem for you. It's a round peg, square hole situation and you can't live with that happily.
I can imagine your heart sinking when you realised she'd has those drinks. Can you keep this cycle up indefinitely?