Sleep help - unfamiliar places

[ladygrey]

DD is a great sleeper at home, especially since we Ferbered a few weeks ago, but is having trouble sleeping anywhere besides her own crib. My mom watches her two afternoons a week and every time she tries to lay DD down in the crib (my parents turned my old room at their house into a nursery) for an afternoon nap DD freaks out, screaming and crying until my mom caves in and eventually rocks her in her arms for a short nap. I explained to my mom how to do Ferber checks, but she doesn't feel comfortable letting DD cry for more than 5-10 minutes. 

I have started bringing DD over to my parents' house earlier in the afternoon to try and get her down but either she is not yet ready for her nap, or does the same freak out with me. It's exhausting to spend an additional hour of my time fighting my own child for a nap. I really need her to be able to sleep in places besides her own crib, since we plan to spend several weekends at our cabin and on vacation this summer (plus my mom needs to stop relying on holding/rocking DD for afternoon naps at her house).

Any suggestions on how to help DD nap in a strange place? She doesn't care for a lovey, won't take a pacifier anymore, and since Ferbering doesn't nurse/take a bottle to sleep. My mom has also tried spending time playing in their nursery with DD to help her become familiar with the room, but it doesn't seem to be working yet.

[speckledfrog]

You have to get your mom on board. DD is crying because your mom goes in to get her. I would keep putting a lovey in with her, my son didn't take to one until he was about a year old.

[ladygrey]

speckledfrog - DD cries even when it's just me (I've been going over there before my mom comes home from work). I do Ferber checks, but she still screams and cries for almost an hour.