I ask this question because on the 22nd we had to put down my little girl, Chiquita. I’ve had her since 2008 when she was a kitten and she had just turned 18 earlier this year.
I was wondering if, since she is now a spirit, she can understand english and what I am saying. And can she also speak to me like my other spirit companions can?
Not in my experience - all non-human (i.e. not human ghosts, ascendeds or ancestors) spirits use the right brain style telepathy, communicating in images, symbols and emotions.
Our subconsciousnesses are variously trained to know how to translate those incoming impulses into forms our conscious mind can understand. If you have trained your subconscious well you can get clairs, but the clairs are not the message, they are still the translation of the message.
im sorry about your kitty. heres my experience and also… this reminded me of something.
I know alot of people might not like david icke but i do remember him having some nature of reality series. he mentioned how human language in a sense has confused people, and that the language of the universe is telepathy. i experienced this once in an OBE. there were times i talked to people wherever i was and we both used english… but… the best way of communication is through telepathy. its the language everybody has but maybe some have just forgotten.
telepathy its like… a big giant packet of data being sent to you instantly. its so much easier than listening to words and trying to decode them. you can connunicate through emotions, telepathy, and through pictures and visions… and i think what we percieve in our third eye is filtered by what we know. and i think it goes for other spirits too. its a little hard to explain but rest assured communication is possible! its just probably not gonna be in an english language. if you do see a word its your spirit giving you that because its a message your cat sent you and the best way for you to understand what you saw was a word thats great! but your cat didnt send you the word its almost like your brain filtered it for you… does that make sense??
your cat can give you messages or any other being but honestly not everything knows an english language.
i experiences telepathy like a huge download of data of what something was trying to tell me and it just clicked… its instant too. it was almost like a computer. and i didnt hear a single word. sometimes human form spirits will smile etc… well whats a smile? or an angry face? etc etc.
its real communication happening! but its different than earth. although i did speak english in an OBE once but its not neccesary.
the telepathy is a lot easier than left brained analysis, breaking down what things mean etc…
i kinda jumped all over the place. your cat is fine though rest assured. 
just dont expect a english language conversation. and in my opinion… telepathy is better, easier, and also communication with emotions. i think most humans have lost touch with this. i suck at grammer and spelling … i dropped out of school … i get called out by spelling police online… but the real language of telepathy is a whole lot more better in my opinion. language can be very fun and cool but in the spirit realm i think language goes out the window and telepathy takes over. but i also still think language is possible… just probably not with something that doesnt know english. god only knows how many languages are out there.
also i met people that didnt know english and we connunicated through pointing, laughing smiling, and using gestures. there are many kinds. but ya your cat is fine just be open to other forms of connunication 
for example if you tell your cat you love her… try not to use words. put your hands over your heart and feel and use intention… of what it would “feel like” to say i love you. and beam it to your kitty using your intention.
I think the most you could try to do is call for Barabatos and ask him to translate what your pet is saying as you meditate.