I've seen quite a few cows that in the very end of their pregnancy show a bit of a rectal prolapse. I've never fussed with them or worried about it when the 'ball' sized prolapse goes back in when they stand up. After calving I've never had any problems with them.
However, I did have one problem with a rectal prolapse this year. The animal in question had a rectal prolapse that did NOT go back in. Ended up with about seven inches of swollen rectum hanging out her back end.
It was a pretty gross procedure pushing that rectum back inside of her, especially since she kept straining the whole time due to the irritation of those membranes. My man and I had both arms up to the elbows inside of her to push it back into place, and everytime we thought we had won the battle, she'd give a grunt and WHOOSH - out it would pop again (in the process liberally decorating us with less than desirable fecal material - ick!) When we finally got the darn thing in a fairly good position, I had to keep my arms inside her to keep her from expelling it again while he sewed a 'purse' sitch around the anus.
Basically, you thread your needle with a fair amount of thread, then make a puncture with the needle beside the top of the rectum. Then you draw the thread through the hole, and make another sliding stich beside the bottom of the rectum on the same side as the first. The next two are similar, but starting on the bottom first and then finishing up at the top on the opposite side you started on. The concept is somewhat like a draw string on a bag. Basically, you leave enough slack so she can pass a normal bowel movement, we left an opening about three or four inches in diameter. Then you draw the ends of the suturing thread together, loop it in a knot and pray the darn things stays put. I was lucky there, because the rectal prolapse did stay in.
Unfortunately in this animal's case, her revenge was to prolapse her vagina. So after putting that back in and throwing some stitches at it, I cut my losses and sent the useless cull to town. She was about two and a half months from calving, and it was obvious that she wasn't going to be able to make it to calving time in any sort of shape.
I don't know if any of this will help you, can only hope it does. Good luck with your heifer.
Take care.