While it is possible she says that she is pansexual because she would like to think gender doesn't matter to her even if it may end up mattering, no one, not you or anyone on YA, can really make that call for her. For one thing, why does your daughter need to have had sexual experience to know she's pansexual when no one demands the same level of experimentation for straight people? Did you need to sleep with a woman to know that you are straight (assuming you are a man)?
It is possible she never talks about finding women attractive because she feels uncomfortable expressing queerness. It may be that she isn't out to everyone. It may be that she has different taste than you.
Also her weight, social isolation, and mental age (not sure what that means or how you figure that out) aren't really relevant to sexual orientation. But it does sound like she might be depressed if she isolates herself and never spends time with her friends and acts angry towards you and your wife. That is unless you are instigating her.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.