I agree with all above she's female. I rely on the tail base thickness in adults. It's not as obvious as it is in panthers but it is a tell.
I don't know of anyway to tell gravid from just carrying infertile slugs. Their body shape changes whether they are carrying either, In females with an uncertain history you just have to expect babies.
Looking at her pictures she doesn't look very well hydrated to me. Have you gone over husbandry with anyone?