My dog loves naps?? what does this mean? ?

my german shepherd is a rescue dog. we just got her about 2 years ago, and the vet thinks she's around 3 or 4 years of age. she's small for her breed and her background is pretty murky. the SPCA said she might have been used as a training dog for pitbulls and other fighting breeds. she was very afraid of people when we first got her, but she's warmed up a bit. she's wary of strangers, but she loves our family. she's definetly my mom's dog though. everyday my mom will lay down to take a 45 minute nap, if she has time. and our dog gets so excited. she'll run around and jump on my mom when she hears the word nap, and then run upstairs, always looking over her shoulder to see if she's being followed. then she jumps up on the bed, circles around a few times, and lays down right next to my mom. we all think it's the funniest thing, that she gets so excited. do you think there's a reason for this? or does she just like relazing with her master? thanks for any comments :] ♥