| Kalvar |
Ask yourself this: If a new guy came to your game (like, say, me) and made that demand, would you give in? If the answer is no, then DON'T make an exception. If you would say yes...Then disregard this post and go for it.
How will a new player choosing to play a goat(that only speaks to one other Player to the exclusion of everyone else) effect the rest of your players at the table?
...this sounds a lot like a @%^& test and she's trying to see if you/her boyfriend are going to cave to her unreasonable "do this or else" demand by trying to get you to let her play the most ridiculous concept she could think of. If you go through all the hoops needed to make it possible, she is going to keep trying to push/break every rule the entire campaign until you tell her "No." in which case she'll have the excuse she's looking for to not have to play. I'd suggest not doing that.
If you still intend on going through with this, perhaps do the Hodor Concept, I would run that character as an NPC. Maybe she'll get into the game and want to be more a part of it, which is when you can let her make a new character. If she then refuses, it's most likely because she really didn't want to play and she just needs to have a reason to not play. In that case, perhaps the goat should get eaten by a dragon.