She is still calling and I'll mention it to the vet when I take her for a "New Pet Check" on Friday.
According to reputable cat sites online, when a kitten is spayed she has not yet begun producing hormones, but as my little Mia is older than that, plus has had a litter of kittens, her body has been flooded with hormones, and the online advice is that it can take weeks/months for these to calm down.
A magnificent black cat appeared at the weekend hoping to offer his services!
Fortunately I have got my garden "cat secured" so he couldn't get in and Mia couldn't get out, but they were touching paws under the gate. Sweet!
I don't think she can be missing her kittens. The foster carers who were looking after her and her kittens had separated them once the kittens were 9 weeks old. Mia's milk had dried up before she was spayed, and the kittens had been adopted when I adopted Mia.
Anyway, she has settled really well with me now, is very affectionate and ruling the roost!