Yep. That's what I was expecting to see...vaginal prolapse.
We used to (don't know if they still do) classify them as Grade 1 through 5
1. Out when they lie down, but goes back in when they stand. (Looks like yours would be a 1, right?)
2. Out when they lie down, usually goes back in when they stand, but sometimes not... but in more than out
3. Out more than in
4. Out all the time
5. Hanging out all the way, with cervical os presented
Used to see those #5s on big ol' Beefmaster cows on a regular basis back in the 1980s... that thing would sometimes be almost as big as a 5-gallon bucket.
They tend to get worse/bigger as time goes on... and worse/bigger closer to parturition, but not all will do so.
It is a heritable defect... I wouldn't advise keeping offspring from an affected cow as breeding stock.
Most breeds that have a history of vaginal prolapse being a problem (Hereford, Shorthorn, and derivative breeds with those two in the mix) have, over the past 30 years, worked hard to eliminate lines carrying that predisposition.
That said, I've seen vaginal prolapse in many breeds - first one I ever saw was in a nondescript black Brahman-cross cow; saw one in a 3/4 Bison-1/4 Brahman cow once.