Hi,
Thanks for consulting us,
You may try water based lubricants like K-Y jelly for vaginal dryness.
But i suggest you to find out the cause of her vaginal dryness first. As this may well cause her trouble conceiving. There are a few possibilities. It may be due to lack of foreplay , psychological conditions like vaginusmus and pelvic pain, pelvic infections, anxiety regarding performance, low estrogen levels and some drugs such as narcotics, tranquilizers, nicotine, alcohol and sedatives.
I think her clinical examination by a gynecologist may give a clue. Doctor may give her appropriate advise & specific treatment if indicated.
Hope this clears your query. You may write back if you want to discuss this further. I will be there to respond.
If you do not have any follow up question please don't forget to accept my answer & close this query.
Wish you good health.
Regards

---