Is gas in cats always bad?

My cat, Trinity, is 4 years old, indoor, and recently has started having gas. Not an absurd amount, but I've had her for two and a half years and she's never had a problem before. I work at night and am home with her all day and she's a stage 5 clinger so I'm pretty aware of her normal routine.

She gets good exercise for only having 3 legs, so I don't think that's it.

I changed her food about 2 weeks ago from Purina One Beyond to Blue Buffalo weight management. She's under 8 lbs, a good size for her body and condition, gets 1/4 cup of kibble every morning and evening, and her weight has a tendency to fluctuate a lot if not monitored

(hence the weight management). 

The vet put her on prescription r/d but I can't really afford it and she has reached her goal weight so now we just need to maintain.

I've only noticed her gas twice or so; it's always in her sleep. I'm not worried since it hasn't been more regular. I'm more curious as to whether there is any actual cause for concern given I did just switch her diet and that seems to have triggered it.

I thought Blue Buffalo was going to be a better choice for her. :-/

Gas is completely normal and healthy especially for herbivores due to the quantity of indigestible carbohydrates (fun-fact: vegetarians produce more flatulence, heh) and a little bit for omnivores, but from everything I have read can be a sign of gastric distress for carnivores and should be considered abnormal and unhealthy.  

And you can have the highest quality organic hand made wheat bread, but if wheat doesn't agree with you, you're going to get tummy upset.   Ditto with the Blue or other good foods, if there is an ingredient in there that's not sitting well, its not a quality issue but still has to be addressed. 

There is a chance though that it isn't the diet at all, but something else as random as an awkward feeding position causing the cat to swallow air.  

They can also be lactose intolerant just like humans. Most of the people around here know better than to give a cat the proverbial "bowl of milk" yet many do.

Don't give your cat dairy products. Give it soy milk.