Hello, Lisa and welcome!
I'm so sorry you're worried about Olive and this gagging you described.
It's possible that now that she's grooming herself PLUS the little kitten, she's ingesting a lot of fur and is having a hairball problem. Giving her a hairball gel like Laxatone or Petromalt, will help the excess hair pass through her system more easily. Also, sometimes, cats just get a 'tickle' in their throat, from some ingested fur.
It's also possible that she ingested a non-food item or something caustic or toxic that irritated/burned her throat and this is causing her to gag. In addition, sometimes, gagging and not bringing anything up, can be a symptom of acid reflux or excess stomach acid coming up into the throat and burning it. You can give her 1/4 of a 10mg. Pepcid AC tablet every 12 hours and see if this helps. This over the counter acid controller, has the generic name 'Famotidine' and can be found in any pharmacy or supermarket. Here is more information:
If she's eating, drinking and eliminating as usual and basically acting like herself, although a little cranky, it doesn't sound like she has an intestinal blockage from a hairball; however, if she is cranky and doing this gagging, she's uncomfortable, so it might be a good idea to have her seen in person by her vet to make sure nothing is seriously wrong.
I'm so glad to hear that your two kitties get along so well! Mainly, I hear how the introduction of a new kitten causes the other cat to attack or hide, and it's not an easy situation. You're skillful (however you introduced them) and lucky, due to their personalities, that they cuddle and Olive is maternal toward the kitten, grooming her, etc.! : )
I hope all will be well with Olive!
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