Do you have a local mart? Our local mart - Carlisle - has a calf sale every Wednesday. If you went along and had a look at the calves in the pens, sometimes the breeder is with them and you can ask questions about its history, has it drunk from a cow, what is the health status of the herd it's from, etc. (TB status, BVD, IBR, Johnnes disease, etc.)
But better to dry her off and breed her again sooner than take risks with a calf of unknown provenance, I agree.
If that's your plan then yes, get her on poor pickings - no cake, indoors on poor straw if necessary - to get her dried up. Not sure whether you might have to draw off just a little to relieve the pressure - but not too much or you'll stimulate production. Maybe use one of those anti-mastitis thingies in her teats? I'd check with the vet whether s/he thinks that necessary.