Some lesbians only want to be with other lesbians, and they would feel betrayed/lied to by her calling herself a lesbian.

Just like women I date would feel betrayed if i called myself straight, but they found out I had a sexual relationship with a man.

We can make up our own definitions of these things, but other people may not agree with us.

I mean I think I'm a straight, but plenty of people in my life past and present tell me that I am gay. Including bisexual women I have dated.