I've not had a female cat fixed.
But my Radar had a hernia repair at the same time as his neuter, 6 stitches down his abdomen, like a zip, with internal stitches holding his abdominal muscles together too. The next day he was leaping back on the bookcases like normal and was just fine, even though he had his stitches in for 10 days - and his incision was longer than spay surgery!
It is natural to worry, I have been in pieces any time any of mine have been in for even simple procedures like neutering (I couldn't sleep the night before, cried from worry when I left them at the vet, couldn't eat all day, cried with relief when the vet phoned to say they were OK, and cried once more for good measure when I went to pick them up, and again when I got them home :o ) - it doesn't matter that rationally you know spaying/neutering is a low risk procedure, it still absolultely does your head in!
So good luck to your little'un, hope all has gone well