Accepting second cat, advice

[Retsina24]

Our rescue cat has been with us 2 years. She's a real sweetie with people but is not friendly to cats and dogs that she comes across when she's outside. She fights with our neighbours cat (difficult to tell who starts it) and hisses if a dog walks nearby on lead.
I would love to add another cat, maybe a kitten, to our family but am guessing it's not likely to work out if she's like this with other animals. Anybody tried it in a similar situation? Thanks

How long is a piece of string OP? This is a problem that has vexed cat lovers since they lived in caves …. there’s no way of telling how personalities will interact. How would you get on if a new flat mate came to live with you without your say so?
Best I can advise is that you choose a confident kitten that will not be intimidated by your DC’s initial hostile behaviour. An adult cat is unlikely to actually attack a kitten and most probably the kitten will continue to make friendly overtures.
Even if the kitten is accepted they may never by BFs, but just tolerate each other.
Try to get a kitten on approval for a few days and if it is obvious DC will not tolerate it ie decides to go walkabout, then you’ll just have to give up the idea.