There’s nothing wrong with flirting, regardless of gender/preference/etc. If you really aren’t attracted to them though, don’t lead girls on. That’s just weird and mean.
There was a girl I knew in college who would flirt with people in extremely come-hither sorts of ways, and then when they responded positively and attempted to up the ante (a physical touch, an attempt at a kiss, etc, etc), she would get suddenly, dramatically weird, and be like “Oh, how could you ever think that I… I was flirting? What kind of person do you think I am?” despite, you know, having just flirted more forcefully and extensively than anyone else at school.
Most of my friends eventually decided that she just liked breaking boys’ minds, but some part of me kind of believes that she really didn’t know what she was doing, because she is a psychopath and just doesn’t make that connection.
So, yeah, don’t string people along.