ways to convince my mother to get another kitten?

Try seeing it from your mom's view.

Your mom may be thinking these questions;

How many cats do you have?

Can you afford shots, wormer, flea/tick protection, and vet visits (when necessary) for your CURRENT cats?

Are all of your current cats spayed or neutered?

Can you afford the current food & cat litter bill?

If you can do all of that then add in costs of one more (add another set of shots, more wormer, and one extra dose of flea/tick protection a month, plus vet). Ask if that's in their budget. If it is then offer to do extra chores.

The shots, wormer, flea/tick protection, and spay/neuter is all needed. Especially if they will be inside/outside cats. Spay/neuter to prevent unwanted kittens that you have to find homes for, flea/tick protection because you can drag fleas & ticks in on your clothes to them, shots prevent certain diseases, and wormer to make sure your cat is worm free so no new problems arise.

Kittens do good with slightly older cats also. It's not always kitten needs another kitten, it can be kitten needs slightly older cat (1-6 yrs old).

Show her examples of kittens and give her hints, don't just come right out with it. Show her MUCH responsibility and respect as you can! Maybe, instead of gifts for Christmas...you could ask for two things, family, and a fury companion! :)

tell her that the kitten needs a companion and think of all the pros and cons to it. make a list and show it to her

i do not know dear, if you tell your mamma you will be totally responsible , for the new kitten, that might help. peace