L.A.
Others may scoff, but this will work.
Run any and all errands in the morning after she has had a chance to play for 45 min to an hour. Give her some juice and a tiny snack, then errands.
Come home have lunch and down for nap by 12:00 or 12:30.. You need to get rid of the afternoon nap.Her nap should go no later than 1:00 or 1:30. Instead have her play outside for at least an hour or hour and a half, running, jumping, screaming, laughing, climbing, pushing, pulling..Make sure she has a trike, has a wagon. Go swimming.
Every thing you can think of.. She is growing and the more activity her body can get, the better her body will feel.
You need to make her room dark with black out curtains, we used quilts during the summer.
While you are preparing dinner maybe Dad and baby girl can go for a walk or he can also have her play outside.
During dinner make sure she eats really well. Turn off the TV and the cell phones. The more activity that is going on the more she will want to stay up and hang out with you guys.
Then give her a nice quiet bath. No wild activities, just calm. When you wash her, use strong wipes with the wash cloth. Like a massage.
Carry her to her darkened quiet room and dry her with strong slow strokes like a massage. Do your routine, but with the singing, it should not be boisterous. It needs to be a time that things get quiet and stay calm in her room.
Get a sound machine or play quite music while you read to her. Do not take phone calls or have the TV where she an hear it. You do not want any distractions that will make her think she is missing out on anything..
She should turn into a "limp noodle" and sleep great..
The more you stick to the routine, it will come naturally to her to start to relax and be tired.
I am sending you patience..