Jim and I found our 30 footer too small for permanent liveaboard
and cruising. The 30' boat in question was a Yankee 30. 36 feet worked for us for 18 yrs., both while working ashore and while cruising.
Most likely, your GF will do a whole lot better if she is involved in things from the get-go, if you think she's a keeper. If not, best break up before it gets to the bitterness stage. Feminists used to say, "Men are like trolleys, there'll be another one along soon." I bet it's the same with the genders reversed. ;-)
If you're the one who knows the most about boats, then she can't be too involved, lacking the knowledge base. Actually, if she's the kind of gal who loves cooking
and "homemaking", find out what she thinks she could do to make it all "nicer." Of that, see what fits for you, then negotiate. You're going to need to keep those skills alive, anyhow.