Thank you for this and your support. Not getting too into it, but they have deleted his post so I think they know who’s in the right...It doesn't make me not support his choice to serve. I have no doubts about the needs of any branch trumping all. It made me hesitate, not about a ring, but about WP not allowing him to finish and graduate, especially considering he made offer to pay for it. We are 100% aware that his desire to serve whether via SA or NROTC means he is no longer 'ours' or available to us when we would like to see him. His sister is aware he may not make her wedding. We have had those conversations. I am still hopeful that the OP can reach a path to graduation. I know 'rules are rules' but when there may be no harm, I believe they should evaluate and make case by case decisions. But, that's just my HO.
Depending on when her wedding is, so long as he can put in an ETP (exception to policy) in a timely manner, he should be able to go. Of course, as you acknowledge, there is no guarantee. My own personal experience with my sister‘s wedding, I was granted to leave Thursday evening and return Monday night (missing two school days and weekend military training). If he is somehow incorporated into the wedding party as well, and family photos are set for a day other than the wedding itself, command is very understanding of how his absence would affect the wedding.