Most Helpful Girl
I think what most nice guys forget is to have confidence within themselves. Nice guys are definitely attractive boyfriend material, but from my experience, most nice guys that I have met are very shy and timid. I think it's cute, but I like guys who have a strong sense of who they are, are proud of it, and have the courage to ask a girl out because they know that they are worth the shot.
Most Helpful Guy
You have to be a "tender defender", i. e. kind to her, but also assertive verbally and physically. She has to feel that you're strong and able to protect her, but also that you're gentle.
The problem about being "nice" is that we usually do it to seduce the woman, but most women would rather have a straight-up guy who is genuinely nice when appropriate, rather than when most horny/infatuated.
This explains it better than me: