Thank you Sue,
First, with the spacing between vomiting episodes, right off the bat, sinister issues are less likely here for Rummy. As well, if she is putting on weight, then chronic GI issues or systemic disease (ie organ dysfunction, metabolic diseases, etc) are also less likely. And I must note, that with the infrequency of her vomiting, we do have to appreciate that this could be normal for her (as some cats are sick every now and again), related to a mild GI irritation to one of the proteins in her diet (if she has a dietary sensitivity), or could even be related to a hairball (as these cause intermittent obstructions that may block food passing from the stomach to the GI before they pass out into the intestine themselves).
So, with all that in mind, we might want to consider first regularly treating with a hairball treatment (which can be added to her food). As well, if you think her signs may have started with a particular diet, you can consider a switch to a sensitive stomach formulation. There are some veterinary ones (ie Royal Canin Sensitivity Control, Hill's I/D, etc) but there are also a range on the market.
Further to these steps, since you are specifically seeing dry food coming back up within a few hours post-eating (which is soon enough after eating that gut motility issues wouldn't be a top concern), I would be suspicious that the dry food and her eating habits could be our culprit. We can often see cats over eat or too eat tpoo quickly and induce vomiting and this is a concern if she feels she has to have her guard up when eating. This is especially something we see when they are on dry food.
This is because dry food expands when in contact with the fluids in the stomach. So, if a cat fills her stomach with dry that then expands, this leads to a very full stomach and often this distension will trigger vomiting. Cats who are prone to this often will vomit the dry food, show no ill effects, and happily have dinner again.
So to rule this out and potentially address this for Rummy, you can consider swapping to wet food (since it won't expand). Or if she isn't keen on wet food, then offering multiple smaller meals or making her take a break during dinner (give 25%-50%, then make her wait 20-30minutes before giving more) to just avoid this situation and halt vomiting from this cause. As well, if she isn't keen on the other cats, then you might consider feeding her separately to ensure she can calmly eat without the stress of a possible altercation (which is why she is wary).
Finally, in case we have an underlying nausea triggering her signs, I would just note that you can also consider trialling her on an antacid. There are a number of antacids that are available over the counter and pet friendly. I would advise only treating with one, but the two I tend to use are Pepcid (More Info/ Dose) or Zantac (More Info/Dose). These are usually given 20 minutes before offering food (to allow absorption) and of course you want to double check with your vet if your wee one has a pre-existing condition or is on any medications you haven't mentioned. So, this too could be a consideration to keep her stomach settled.
Overall, her signs are quite mild, and I'd not be overly suspicious about serious health issues with Rummy's history and vomiting infrequency. Therefore, I would advise keeping up on your worming, considering hairball treatment to remove this as an issue, and taking the above steps relative to her diet. If she does still show nausea, you can try her with an antacid, but overall her signs are quite mild and more suggestive of a low grade GI disturbance then a serious health issue for her.
I hope this information is helpful.
If you need any additional information, do not hesitate to ask!
All the best,
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