Wendy said: First of all, having precancerous cells in the cervix rarely, if ever, impacts fertility. That being said, this condition needs to be dealt with prior to conception, as obviously nothing can be done to the cervix during a pregnancy, should a procedure be needed.
Some vegan women are overly lean; one needs to have enough fat / body weight to give the message that the world is ok (no famine!) and it's ok to get pregnant. And if you recall, there needs to be enough cholesterol in order to make the steroid hormones. That's not how much cholesterol she's eating, which is likely very low, but how much is her body producing. So I would need to see a lipid panel and an omega check (measure of omega three fatty acids) to see if diet needs to be adjusted. Many vegan women conceive normally/easily, so I hesitate to say it's her diet unless she's too extreme.
There are so many other things that could be going on. Could be the male partner! Could be tubal occlusion, could be many other things. That is about all that I can say based on the limited information provided.