Calliope gets constipated every now and then.

If she is still backed up you will feel that her belly is a bit hard and her poo will look very dry.

There is a cat laxative in a green tube available from vets and good pet stores. If you spread it on her paws, she'll have no choice but to lick it off. Calliope has never had a problem with the taste and it works rather well.

If your fur baby is walking a bit stiff or looks uncomfortable I would honestly suggest popping to the vet and getting them to put in a suppository. They might also do a gentle enema.

We had to get both done for Calliope once because she was so backed up, poor thing, and once they had both worked, it was like she was a brand new cat!

I would suggest the diet change affected her a tad, yes. It's not uncommon.