Hi Ella19 and welcome to the forum !
I want to say immediately that this situation is more complex than introducing two unrelated cats to each other.
It might help resolve your frustration (and, I suspect your boyfriend's) with this new behaviour if you were to try and put yourself in your kitty's situation: her entire world - as she knew it - was taken away from her, and she has found herself in brand new, unfamiliar surroundings (remember, she only has sensory
perceptions, scents, odours, 'smells', aounds etc. ...she cannot rationalize
the situation as you might/would).....and, on top of all that, there's this strange cat she's forced to deal with (after, presumably, having previously lived by herself). I'm not at all surprised by her response to all this.
It's very sad that she has been so upset that she has been incontinent
I'd say that you need to give her her own space
in the apartment - perhaps one room could be hers and the new cat kept out from there...? She really needs a safe space for (at least) a solid/lengthly period of time allowing her a real opportunity to adjust and settle. That separate space should contain her own food, water and litter facilities......I would put any and all of her own "things" in there with her along with something(s) from your old place (preferably things that hold scents) that she's familiar with. (I think you should do this without a timeline
attached. It may take an extended period of time for her to settle in. Allow her to tell you
when she's ready to expand those boundaries.)
I hate having to discipline her I would just let her know she did something wrong and put her in her cage for a little bit.
Now, to me the very thought or suggestion of that is even more disturbing. She's done absolutely nothing wrong....none of this is her fault! What has happened/is happening is the result of humans not understanding what such a change can mean to a cat
and consequently not adequately managing the change from the cat's perspective. (I'm not blaming, btw...it's "simply" a question of "Who knew?") I once had the same experience as you: A long time ago, I made a major move with a cat....and learned a lot as a result - all of that learning came during and after the move
, so I do have an understanding here.
I'd also suggest that you "delete" the concept of "disciplining" cats.......it does not "work"....period. (and, that's not even mentioning the cruelty involved!)
I'm hoping that helps !