C.! Hang tough, it's OK! My 11-year-old daughter would love to play with yours and would be all over her American Girl furniture. Can she bring over her AG dolls?....
My daughter is the same age (nearly 12) and though she doesn't play with Barbie -- well, she never did get into Barbies at all. What she has covering her bed right now is stuffed animals. Not random ones but ones she has gotten since she was 10 months old. I gave her a new one for Christmas because she fell instantly in love with it in a shop (and did not ask me to buy it then and there but just looked at it with such longing that I went back and got it and kept it for months waiting for Christmas). Each animal has a definite personality and interests and activities and believe me, her dad and I talk to and have adventures with the animals too. So...your daughter is not at all unusual (in my book!) for still loving toys and pretending and playing with them.
I bet that if you really eavesdrop on your daughter's play you would find that it is more mature than you realize -- the stories she plays with her dolls etc. are likely more complex and interesting than they were a few years back. That's great. Toys are still stimulating her imagination and there's nothing wrong with that!
But you have the issue here of your daughter both wanting her toys and being embarrassed by them. I'm so sorry that she's somehow become self-conscious about the toys, and I hope that her embarrassment wasn't driven by some "friend" making an unkind comment about what was in her room.
I would tell her that everyone has "toys." Adults have cars they worship, or electronic devices they use to play games. Some adults collect toys all their lives and though they may not play with them, they treasure them and put them on display for everyone to see -- so having toys out in her room is kind of like that. With AG dolls and furniture in particular, those are collected by older girls and adults. I see girls who are clearly at least 13 to 15 in our nearby AG store -- carrying dolls and examining all the goods. No shame there.I bet if she puts the dolls on stands when she's not using them and displays them, she can tell other kids with great seriousness, "You do realize they are collectibles, right?"
Is there any place in your home that can be her playroom where she can put larger things like the Barbie Dream House? I can see another kid making fun of that, I'm sorry to say, but I'd certainly defend the AG items as big-ticket collectibles. I tend to want to say tell her to be proud about her toys, especially anything someone lovingly MADE for her! But I also get her preteen embarrassment factor. So ask if she wants her room redecorated but I would not add "because we can put the toys away." Make it more about the fun of redoing her room, not about making it some rite of passage where she has to get rid of toys (though that may end up being what it is).
I admit that this advice comes from someone who loves her kid's toys. They are family members. It will break my heart a bit when my daughter no longer sleeps with her old Kitty toy in her arms (as she has since infancy). I go into her room some days and arrange the animals in amusing ways (the other day they were in a circle, playing blackjack and apparently wagering, for shame! She liked the joke). She even has assigned toys to my husband and me, ones we must keep in our bed and which mysteriously end up in the car going on trips with us. Just yesterday the new animal, a very realistic black bear, came in the car with me when I went to pick her up at school - just because I thought he needed an outing!
Sorry to digress into toy-love. But all that is to say -- it is wonderful that your daughter enjoys and gets use and fun and comfort out of her toys. Toys require more imagination and effor than mindless staring at tiny screens so your kid is making a good choice. I just hope that she can be strong enough to shrug and say, "I like imagining things, and these are my tools for imagination. Any real friend of mine won't snark at it but will play too."