She "should" lamb ok with harness and/or spoon. Personally I would use one or the other but prefer the harness as not poking and irritating sensitive tissues, potentially risking infection.
If you can take the spoon out without her prolapsing, then do.
Uterine prolapse may or may not happen afterwards, frequently vaginal/cervical prolapses lamb fine and with no post lambing prolapse, and plenty uterine prolapaes are not preceded by a vaginal prolapse, but you would be keeping a close eye on her anyway so would catch it if she did have one.
And retirement is a good plan as she may do it again.