Giselle/Robert/Nancy love triangle-poorly written?

I love the film Enchanted but there were something that bugged me about this love triangle.

First of all, the romance between Giselle and Robert came off as one-sided romance. On Giselle's side, you see a lot going on. You can tell when she started falling in love with Robert and how she did not want to hurt Edward's feelings.
Robert's side; not really. He didn't seem to like Giselle at all (at least in a romantic way). You can't tell when he started falling for Giselle. Even after the "So Close" number, he acted like he liked Nancy better. Also when Edward told Robert to kiss Giselle to save her, instead of immediately kissing her, Robert freaked out and protested. Seriously, what is with this guy!? There is a difference between kissing for love and kissing to save someones' life! I'm sure Nancy would understand. If Aladdin can suffer a little watching Jasmine kissing Jafar, I'm sure Nancy can suffer a little watching Robert kissing Giselle.

Second of all, I felt that the movie didn't give me a clear explanation why Robert decided to marry Giselle instead of Nancy. The problem is that both Giselle and Nancy are nice girls who genuinely love Robert for who he is. The movie failed to tell me why Nancy was not a good match for Robert. It also failed to tell me why Morgan liked Giselle better than Nancy. I would have like the movie a lot better if Disney made Nancy evil or at least threat toward Morgan and Giselle.

Either have Nancy be the typical clingy girlfriend who got sooo jealous of Giselle's closeness with Robert that she teamed up with Queen Narissa to kill Giselle.

Or have Nancy complain to Robert how he's never romantic with her-which pushed him away from her. Additionally, have Nancy's attempts to bond with Morgan always fail. After her last failed attempt to bond with Morgan, Nancy grudgingly decides to send Morgan to a boarding school for the rest of her life after marrying Robert. (Like how in the Sound of Music, the Baroness planned to se