While it is true that some women have smaller vaginas that may cause sex to be painful or even impossible vaginal dilation is NOT a "BYU" thing.
I can imagine that since girls get married so young in the church it may be a more common practice amongst Mormons than it is for the general public.
Please consult with a OBGYN for medical advice.
With that being said, I'm turning off the comments on this post because:
1: It's not a BYU recommendation or even suggested by any University that I know of.
2: It's not ExMormon related.