My step-daughter told us she was bi, and that she had a girlfriend. Now mind you, this girl thinks that she should only have the best, and of course, having a bi step-mother made it seem romantic to be that way too. I doubt her bi-sexuality, only because I have only seen her date boys, and her "girlfriend" lives in another state. I have seen this fad spread, because it is cool and the guys think it is cool to have a bi girlfriend...and it is sad. It gives those who are truly bi a bad name, and makes us look like we can choose our sexuality.
People are born gay, it is biologically proven, and bi-sexuality is hormonal, so chemically proven as well. If it is a chosen thing, it quickly dies out once an encounter happens, and distaste is found. I think before posting that they are bi, they should have had a true sexual experience beyond a kiss to prove as such. Leave it alone, and only when you have the experience of being able to say legitimately that you are bi-sexual.