hypersexuality bipolar disorder

Cheating and Bipolar Disorder?
my brother’s g/f of eight months cheated twice on him and he says that its part of the disorder that makes her cheat, but wouldn’t hypersexuality just mean she wants it all the time from him without going out to clubs after work and hooking up with random guys
I in no way believe BiPolar disorder
CAUSES cheating but hypersexuality seems to be the underlying reason that she is acting this way
it is not simplpy hypersexualiy with bipolar, there is a loss of rational thinking, loss of self control, loss of moral value.
i said “loss of __” but it is more like a distortion of normal functioning.