because if you like both genders, you like men as well? that same being said as "i like women as well." some bisexuals also have a preference in different kind of attractions in both genders.
Tbh, I can't decide, if I'm bi or gay, I'm mor winto guys, but I accidentally becane bi, now even knowing that (and it all started from my avatar on Polytoria)
Also, I don't really think that revenge is needed, she can be happy with girls