Thank you for the description.
Yes, this could indeed be from being over lubricated which has resulted in irritation. But we can only assume thos once all causes for such a presentation habe been ruled out.
As she is pregnant she will be experiences many changes in her body. In such a scenario it is best to visit her obstetrician to rule out any abnormalities and get the required attention she needs to be comfortable during her pregnancy
Hope this helps.