Yeah its cheating considering the intent. What happens if the other woman takes it further and wants some hairplay that leads to sex?

Personally, I've dated a women who I told her I liked long hair, then after we got comfortable with each other, I told her the full extent of my hair fetish, which is very sexual.

She was very open-minded about sex so it didn't take long to have her understanding about it.

I shared everything including websites and porn. While I didn't expect her to have the same reactions I had about it, I didn't revolve our entire sex life with just my preferences. She had thing for sex in the pool or having her pussy f*cked with water hose. Sex in the shower was a big thing for her. It didn't do much for me, infact I hate wet hair. She would try her best to stand in the shower and not let the water get her hair wet while we were having sex. Yeah it made for weird positioning but we wanted to please each other.

My advice is be honest with her, tell her everything and try NOT to make it out to be that its the only thing that excites you or that you absolutely DO NOT need to be gratified by using her hair for your hair fetish.