The issue of risking a friendship to attempt a romantic relationship is always fraught. One of my best friends was a girl and I avoided expressing any romantic interest in case things didn’t work out. We’re still good friends and I have a different gf.
I don’t know if your friend has any relationship experience or not, but I do know a few people who thought they were asexual until they were in a close romantic relationship, then discovered they were actually demisexual. It’s difficult to determine which one is, until they’ve been in a relationship.