Sleep for babies makes more sleep, I had my 5 mo twins to bed at 7pm then wake at 10:30pm to give one more bottle of milk and then they slept until 6am. Feed small bottle 3 oz and they would go back to sleep until 8 or 9am. Then Feed 4-5 oz, then put down for a nap at 10:30am , Then tummy time, watch a baby einstein or play with toys, Do you have a vibrating bouncy? I used this as a short nap for an hour or so. Then vibrating bouncy time so I did housework in the mid morning and early afternoon naps. Nap at 12:30pm Some of these naps should be in her bed some in the vibrating bouncy or pack and play. The Key is you feed and lay down, they know if they are getting fed they are sleeping. And have playtime/tummy time in the morning when they wake up for the longest amount of sleep first thing and again late afternoon. after several naps.
Put her down at the same time everyday her body will adjust and crave the sleep she needs, if she isn't sleeping she is got to be cranky from the lack of sleep and thus not sleeping well the times she is sleeping. She needs deep sleep, the only way to acheive that is sleep cycles of rest that her body is used to . Eating then sleeping is telling your baby thats what you want her to do. You have to stick with it, and the vibrating bouncy, and shhhing with soft voices and rubbing their head instead of rocking/holding to sleep is key. Rocking/holding is sweet, but its the transfer to the bed from your soft arms that keeps it from being successful because they'd rather be with you. Soothing with music, rubbing head and in their bouncies was great for twins but also for their sleep as I couldnt coddle them to sleep and they learned self soothing much quicker. Do you use a paci? Only giving the paci for sleep times helps them understand its special for sleeping and a soother for them as well.
Good luck routine is key and sticking to it, children thrive on a schedule and routine its their safety and your sanity no matter how repititive it seems.