Question about mounting behavior

It is perfectly normal for girls to mount each other it's part of their dominance behavior. But in case you want to check again here's a good sexing page:https://cavyspirit.com/sexing.htm

Females will also rumblestrut and mount other females, as either a dominance thing, or when they are going into heat. It's not unusual.

Yes, it's totally normal. Humping is a normal part of establishing dominance for both boars and sows. You do want to check French Fry thoroughly for a penis to make sure, though. How old is she? Is she having any hair loss, crusty or enlarged nipples, or discharge from her private parts?

OK so I popped over to the CavySpirit's sexing page and looked at the pictures with her in front of me on the computer desk. After some fussing because I had to hold her on her back which she doesn't like I've seen she's 100% girl. I was worried about a week or so ago that she might have been pregnant when we got her too, but I feel no babies in there and even though her nipples are slightly bigger than they had been before she would have had the babies by now. We got them after my son's first birthday in April. Sometime between the 6th and the 20th. They were 8 weeks at the time and as I said before I got them from a pet store. Had I known then about rescues I would have adopted one. When Cookie had a baby I panicked and did tons of research which landed me here. Cookie is 100% girl because she had the baby, the baby...based on CavySpirit's sexing pictures is a girl as well. And I've checked her over and over too just because I wanted to make sure if she was a he that I got her into her own cage before she was old enough to get her Mom pregnant. (If she was a boy that is) It's good to know that it's normal behavior. Part of the dominance establishing. Now that Biscuit is weaned all the way and getting a little bigger I guess they're just trying to establish the pecking order. Thank you so much for all your help!!!