"Is it because I am a girl?"
No, it's because you claimed sums from the public purse which increased your net worth. All reasonable electors accept that MPs should not be worse off because of expenses necessary for their job. You, however, are alleged to have colluded with your husband to make contradictory claims which increased the value of your private assets at public expense. My advice would be to shut up now and consult a criminal defence solicitor at your own cost.
HM courts aside (for the time being) the "court of public opinion" has adequate proof from the clip played on HIGNFY of you hanging up on a radio interviewer who asked you about the claim a couple of years ago. You are politically finished, no matter how agreeable a friend you are or how many good deeds you may have done in the past.
At least your husband knew when the game was up. Stop making him look good by comparison (and stop making your naieve, too-loyal friends embarrass themselves and jeopardize their own political careers in the vain defence of yours). You are helping no-one, least of all yourself.
Resign and stop pulling others (including your party and its leader) down with you. Let your constituency party try to retrieve the situation before some fascist or dimwitted celebrity is elected in your place. You owe your constituents that.
She's standing down, but still protesting her innocence. It never occurred to her until this furore that she was doing anything wrong. Hmm. I wonder why she hung up on that radio interviewer then? Still, credit where credit's due. This is a closer approximation to the right thing.