I don't have a whole lot of answers for you. I think though, that there's always going to be someone that thinks something stupid or wrong about you.
I think the answer would probably to make up your *own* decision and realise that they either don't know you very well, or they're just trying to hurt you and therefore not a great person to mould your perspective on.
For instance, my mum has spent years telling me I'm stupid/ a liar/ etc etc. I've been told to just look at the facts and try to understand that she does this because of *her* problems not because it's true. I do find it hard to believe that, mostly because my facts get skewed because I've been told it so many times.
because yes i can be a bitch if i'm grumpy.
it looks to me that you *can* distinguish the facts.
Ask yourself:
What's your definition of a slut?
Is it the same as the person's who is calling you this?
Forgive me for using such a cliche but, there's that old saying "those who mind don't matter and those who matter don't mind". If this person is calling you or anyone else a slut... is this really someone you want to base your opinion on?