Pre-lambing vaginal prolapse is not uncommon in commercial sheep. Keep an eye on it, if it starts to
not go back in when she stands up and moves around then you may need to do something to stop her everting the vagina completely.
Being such a wee sheep, you wouldn't want to use a prolapse spoon

. Whether a regular prolapse harness would be overlarge, or whether you could get a petite one, I don't know. Otherwise it'd be the vet for a circular suture which you would need to cut when she starts to lamb.
Generally it is thought that the pre-lambing prolapse is caused by the ewe running out of room inside. If she's carrying multiple large lambs, and trying to eat enough grass to feed herself and the lambs and make milk, and especially if she's a little on the fat side, reducing the available space even further, then eventually there just isn't enough room! So in later pregnancy it can be very important to feed sufficient cake that the ewe isn't trying to cram overmuch bulky forage into a decreasing space in order to get the nutrients she needs.

Ironically sometimes you may need to feed a fatter ewe more cake than a thinner one, as she has less room for bulky forage! (Which also explains why it isn't only thin sheep which get twin lamb disease

)
All of which generally applies to commercial sheep rather than primitives. Especially primitives carrying purebred lambs.
So I regret to say that in a primitive carrying purebred lambs, and that is not overweight, I would be concerned about dead lambs.