I totally relate and understand why it can be tiresome. I will say that these sorts of very in depth obsessive interests are not uncommon with gifted kids though and that in isolation from other flags would not suggest Asperger's to me.
Also, while it may not help now, let me offer as encouragement. Our child was much like this as a preschooler as he got older it is fantastic. He's focused. He's creative. He's driven. Hard to take in a four year old but fantastic in a teenager.
My suggestions:
1. Focus on you. Do you have stuff in your life at home that you really enjoy? Are you learning something new? If not I would strongly suggest trying something new - knitting, woodworking, etc. It will help your daughter see that sometimes you need to focus on your own stuff just like she needs to focus on her stuff. Also, I would make sure if at all possible that you are getting out of the house kid free breaks often and using that time for something really relaxing - not just running errands.
2. Clearly communicate your limits and give her notice ahead of time. It might look something like this: "It is 9:30 now and I can play Beatrice Potter until 10:15 and then I need to do laundry. Let's set the timer for 45 minutes. When it goes off it will be time for me to be done." The grim reality is that yeah, you probably have to engage in this kind of play more than you want to, but you don't have to do it all the time. It is important to kindly talk about the limits of other people and this is much better than losing your temper later because you are irritated with it.
3. She needs to have some time exactly as she wants it, but some of the time you can work on gently expanding the boundaries to related but slightly different activities. Perhaps she'd like to dictate a story for you to type on the computer and then you can print it up and she can illustrate it and make copies for the grandparents. Maybe she'd like a tape recorder to tell her stories and then she can listen back to them later. Seeing some plays helped our son get the idea of putting on shows which involved a lot of time preparing on his own so that cut down the parent centered time. It will give at least a bit more variety to her world and be less boring for you.
My closing thought... As the expression goes: The days are long but the years are short. It may seem hard to take right now, but you will miss it. So, extend yourself to more of it than you want to. Take lots of video and photos. You will miss this someday.
