It doesn't look like a "slug" at all. I think you are right, it is an egg.

We did give her a bath but could not wash off all the blood. I was afraid to hurt her but she did not flinch at all. Did not act like it hurt when I was rubbing the spot under the warm water. I did not use anything except water. I bring her in the shower with me sometimes, when she doesn't shed completely. She always seems to like it.

Do you think she might lay more?