For the most part, once the ring is in, it's in. A couple of times, though, it's come out of Alexandria during sex. When that happens, she just puts it on the bedside table til they're done knocking boots. Then she rinses it off and pops it back in when they're done. As long as it's not out more than 3 hours during each cycle, she's covered the whole time.
It's really simple—it can't go too far up.