I think that the best thing you can do for her is just to be there. She'll feel better if you are with her. The anti-inflammatory injection has a pain-relieving effect, so that will be helping too.
Not all groomers empty anal glands as a standard procedure, so I don't think that your groomer should have assumed you wanted it done as routine. I certainly wouldn't. We did once have an accident at the groomers with our first cocker, she nicked Lucy's paw whilst trimming underneath. She was very apologetic indeed and paid the vet's bill as a matter of course, we went straight to the vet, the groomer went in with us and asked them to send her the bills.