Baby feeding at night...

Should I be getting her up when she fusses or waiting until she cries out? Occasionally she will fuss and wake me up so I get her to feed her but she stays asleep and sucks for like 2 minutes before being out like a light again... I've never waited for her to cry or anything because I get scared she wont go back to sleep... but am I getting her when I dont even need to? Could i be getting more sleep ??? She ends up staying in the bed with me from the first time I feed her because I fall asleep and dont move her back to the bassinet so I doont even know how long she sleeps for as she will latch to my breast while we both sleep. I dont wake up to it and she just drinks a small amount and comes off again (my SO watches us some nights and says this is what happens)