While late to the party, I would have said in Zhara's favor for not being a lying gold-digger, as an egg-laying race, she likely knows when she's got an egg needing fertilization and would know when that happens. Also the fact that she makes several visits to you in Hawkthorne at the risk of her life and potentially her child's just to allow you the chance to spend some time with Mitra (who there is no doubt she loves and cares for) would be a strong indicator that she (or any harpy) would just risk their lives or a child's life to 'trick' the MC. Especially when it isn't needed, if Mitra wasn't your daughter, Zhara would be confident enough to assume she could have a child with MC at any time.
As for GF, Zhara doesn't have enough relationship stuff for me to pick her over any other girl with more date-like interactions.
Same deal with some other girls like Zo are spectacular as characters and women but she doesn't really do much outside her little clearing, same with Senja or Meira, we can get them out of Evergreen Manor a bit, and they have potential possibly. Same issue with Hellhound in the Temple, something about her...
Etheryn definitely was my #1 for so long, what with the interactions as well as events like Christmas and such in Winter City, but her lack of... certain opportunities (and knowing that won't likely ever be available) has really pushed me to the cowgirl.
Only recently got Brienne on my Dark Knight playthrough but she is so amazing and so spectacular. I do have her with piercings and bell, which I suspect ramps up her libido, so I do have to deal with the 1-3 page sex scene events that crop up in the world as in the Frost Hound, but I still love them. The village scenes were so much different than on my long-play good-guy main character.
I do consider Riding Eubicha to equal a date, and she is just so amazing in her black maternity top. Like the Tanuki daughters, it's just not enough interaction to put her over the top. Otherwise, Lyric (girl) was such a fun character to play with and interact and talk and listen to, she would contend with any of the companion girls.