I recall, back in the 1980's, in our congregation, 2 single female members who were best friends. Both were physically beautiful and with great personalities. One was the daughter of an elder, the other's father was not a JW (her mom was). As they approached their late 20s and it was apparent there were no suitable prospects, they happened to meet two fellows that were not JWs and were also best friends. As the relationships progressed, both couples decided to get married. They brought their beaus to the meetings, the fiancés had bible studies (with the elder) and they were going to get baptized--blah-blah-blah.
The elder's daughter saw fit to go and get married before her beau's baptism took place and NOTHING happened to her. Bride number 2 started to plan her own wedding, inviting many the same friends that attended the elder's daughter's wedding (said elder having performed the ceremony).
Boom-the special needs talks start up: there were three of them in two months: That we shouldn't date unbelievers, that we shouldn't associate with sisters that do, that we shouldn't attend such a wedding between a a sister and an unbeliever, that the bride-to-be should be marked, etc.
It was so horrible that under threat from her mom that she would not attend their wedding, the second bride and her fiancé postponed their wedding until after he got baptized. Everyone talked about how faithful she was and how she was rewarded. But I thought everyone was a bunch of hypocritical bullies. I was about 15 and decided then and there that I would never mark or shun anyone, and would associate with any and all who treated me kindly and wanted to hang out. (Of course I eventually got marked and shunned for that attitude.)
Oh, and that elder's son-in-law? He never did get baptized, the elder's daughter was never marked or shunned, and the elder retained all of his "privileges."
So that's what the elders might do about it.