I can check.
No, you can't marry her.
If you're on PC you can. If they don't have a unique voice.
I had the same dilemma for my character. Ysolda kept following mine around Whiterun so I chose her. But, ended up going back several saves and staying single a while longer. I'm sure my character will find someone better

I don't know most of the ones mentioned so far but will check them out when I get further into the game.