Ok, presuming she is up by 7.30am, she goes about 3 hrs before a nap, then another 2 1/2 - 3 hrs before her next, then almost 4 hrs until bedtime. Maybe tea at 5.30, then bath at 6pm, then bed by 6.45pm, story then sleep. This means she is only going the 3 ish hrs again.
Is she walking?
Even crawling, you can physically knacker her out, help her climb the stairs before bath, she'll be tired!
What does she eat at tea time? Make it a carb tea, pasta, potato stuff. Not as much protein. Yoghurt for pudding?
Does she have a dummy? If possible, only give it to her as she gets into her cot. Ue it as a sleep cue.
Does she sleep in her cot in the afternoon?
Make sure there are no distractions, no toys that she'll want to play with. Are the curtains thick? Is she in a sleeping bag?
Can try gradual withdrawal, worked with DD1 at about 12 - 14 months. Stay beside her cot, don't make eye contact etc. As she gets used to you being there, move fiurther away each night. Keep lying her back down, and say "sshhhhhh" if she gabbles!
It is so hard, worst thing about babies really. And what works for one doesn't necessarily work for another. Even worse, when you move them to a bad you may have to start again!!!!!!!!!!!!!