Not sure whether to teach my gf dominion. Leaning towards not...
gz dude. gg ez.
Go for it pops! I would just suggest being as helpful as possible without making her seem like she's not smart. Let her read through the cards and offer helpful comments before the game begins. For me this is usually stuff like, "If your Ironmonger hits Great Hall you get both bonuses because it is dual-type." During the game my fiance will often ask me what I would do in a situation. This runs the risk of the game then turning into Me (her shuffle luck) vs. Me (my shuffle luck). But you can get around this by answering the question and providing the reason why. If you explain your reasons you can answer future questions by indirectly by addressing the reason and not answering the question.
This imo is the best way for people to learn. As an organic chemistry lab GSI you never spoon feed answers to students. Instead you guide them to the correct answer by asking your own questions. This ultimately leads them to a greater understanding of the correct answer.
The same can apply for Dominion. She'll have a more enjoyable time because she is learning. And through your little bit of guidance she will begin to answer her own questions of what is best on her own and make the correct call.
I'll be completely honest when I say that Dominion with my fiance is a huge paradox. I absolutely hate losing but I just get this smile when I lose to her because I love that I can play Dominion irl with my best friend and have her play at a level which beats me from time to time.