If they are in contact, the male might have pissed on her to mark her or tried to mount her on her side. It's not rare for a neutered male to still display hormonal behavior when they are in contact with an intact female.
I never tried starch or oil, I would be worried about making a mess. If the rabbit really can't clean herself, there are shampoos for rabbits that work well. It's not recommended to clean a rabbit often, but sometimes you have to (I have to do it with Tybalt sometimes as he developped pododermatitis from not cleaning his back paws which leads to 'dreadlocks' with poos stuck inside if you just leave him be). It works very well. You just take a small basin half filled with warm water. You just wet the side of the rabbit, shampoo, rinse (trying not to wet the rabbit more than necessary) and dry well with a towel. I do everything sitting on the floor, with the basin in front of me so the experience is not to scary (and that I don't risk injuring my bunny if he wriggles free). Your rabbit won't like it. Most rabbits don't like to be handled in the first place. But she'll live ^^. My rabbit generally hates on me for an hour or so afterwards, but his hair is clean and soft again.