1. I'd mouth her...10 to 1 she has a broken tooth or two that are hurting.
2. If she is eating that much and not holding weight, could be parasite or disease.
3. We have never had lice that bad but I can't imagine that is the issue. Could be wrong but...
4. Have you changed your wormer/delicer/fly pour on? I might...in case she has something drug resistant.
5. I'd let her raise the calf a bit from here but i think the overall advice we would have is she is going to start making less profit or actually costing you money. Just a cheap to feed a younger, better cow.
6. The embryo idea is an interesting one. We don't do it so i don't know but can you get really, healthy eggs out of that old a cow? If you went this route, i'd grade them for sure.