Its also possible that she ovulated and you just didn't notice it because she may be full of slugs. When a female ovulates and there are no viable eggs, the ovulation can be very small. It would also be difficult to notice them by picking her up the way Deborah mentioned if there are no viable eggs in her. You can palpate her and feel them in her. You may think that they are just follicles but it could be small slugs like this one.
I thought at first you may have been talking about expelled follicles, but after the pic, its obviously just a slug.
My question now, is did she actually lock with the male, or did you just put the male in and didn't observe an actual lock? Typically a gravid, especially about to lay (slugs or eggs) won't lock up with a male.
I hope she's not full of slugs, but to me it sounds like that would be your most likely scenario. Let us know how things progress.