RP is making me uncomfortable, what can I do without seeming rude?

Background Pony #8678
So someone on Discord asked me to do an MLP RP with them, and I agreed, thinking “Why not? None of my other friends are into MLP roleplays, so it’d be nice to get some use out of my many many characters”.  
I showed her a couple of my OCs, including Pelion, who is rather shy (made, I think, clear in the picture).
 
Well, she suggested that she roleplay Noah, from the TribeTwelve slenderverse series on Youtube. A human. He would be transported to Ponyville and become a pony. I suggested I use one of my Creepypasta crossover ponies, since it’d be more fitting, and I have no problem with doing crossovers, but she said Pelion would be fine.
 
Well, cue the start of the RP, and Noah is screaming in all caps right off the bat. I make it clear (with lots of stuttering) that Pelion is quite disturbed by the screaming unicorn, and she has Noah scream and curse fanatically, even becoming aggressive with Pelion.  
Noah then becomes aware that he’s in a TV show (???) and asks for Twilight, suggesting she might be able to change him back. Naturally, since that would immediately end the RP, Pelion says she’s in Manehattan, and unavailable. To which Noah calmly responds “okay, well, I need a job”.
 
I could just swap him out with a different pony that would work with such a situation better, but she apparently specifically wants Pelion for some reason. This is my first time interacting with this person and I have no idea how to react to this. Right now, I’m resorting to pretending to be busy while I try to comprehend my situation. She seemed really insistent and eager to RP with me, and I’m really not sure how she might react if I confront her about it directly. I’ve never had an RP partner that’s quite this…. aggressive, I guess? Or at least, roleplayed that aggressively. She seems perfectly fine OOCly, if not a bit excited. I have no idea what she’s trying to go for in this roleplay.
 
RP in full
Sherem

in Personal experience, when you are already uncomfortable with an RP, it would mean that you don’t have the drive nor the will to keep going. I would say, don’t be afraid to cut it, but if for some reason or another you still wanna keep going on try get your partner to a compromise, you will have to let go of the idea of “being rude” and do what you have to do. Otherwise you will be in for a rough time, trust me.
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