Rebecca,
let them know that not getting back to you on a timely basis made you and your sister very uncomfortable and anxious. Ask them what you or they can do to prevent this from happening. Find out whom your go-to person, or two is, and maybe get a cell phone number. Get phone numbers in all places that she may be. Best of outcome to your sister. We've been there and are all here to help and support.
All the best,
Rob