Okay, so let's get something out of the way;
The ladies of the Silver moon sect are not virtuous.
Remaining 'pure' is not a prerequisite for them to be able to divine.
Members of the sect were allowed to have sexual relations.
Many of the maidens in the sect already had partners to satisfy their occasional sexual urges and at some point, as was 'inevitable', they would reach the limit of progression in their cultivation.
A condition that would be made known by the speedy aging of said member and they would then 'graduate' which was just a kind way to say they would be kicked out.
They would be kicked out for aging.
For not being capable of eternal youth.
When they reached this milestone, the members would usually then settle down with their partners and finally begin a life. One in which they will be awarded prestige befitting of a once-upon-a-time member of the Silver moon sect.