Why is this happening....?

My daughter is 7 months old, she still isn't sleeping through the night and I am up and down alot of the night trying to get her back to sleep etc. However when she is round her Grand parents for the night, where she has stayed about 3 times in their travel cot she sleeps all night through or close to. I mean their travel cot is close to the floor and looks cosy but not as cosy as I make her cot bed we have at home, even tried it less cosy and no changes. To top it of she stayed round her Auntie's on friday in the travel cot and slept through again. I feel like they must think I lie as my partners Mum says to me when I moan oh she does sleep all night through but when she is at home she really wont. Help or explanations please, im going insane! thanks Xx