Sounds like you have a sleepy bub on your hands! A good way to get your bub into a good day/night routine is to do a feed/play/sleep cycle during the day and then just let her sleep as long as she wants o'night. It takes a while for them to get used to staying awake during the day. I used to put my DS straight on his playmat after a feed, if he was asleep he would soon wake up being on the floor. Sometimes I would bath him just to keep him awake. Your bub can probably only handle up to 45 minutes of wake time (including feed time) at this age so be careful not to over do it either!

If you keep persisting it won't take long for her to work it out. Good luck