Being FF doesn't have anything to do with it, neither do solids (sorry ). Yes, formula feeding does fill their bellies up quicker than breastmilk, but it doesn't necessarily mean they sleep longer.
When you put her to bed at 7pm, is that after dinner and a bottle? Have you thought about removing the dreamfeed at 9pm. To me, if she's having a bottle just before bedtime at 7pm, she wouldn't need a dreamfeed. She may wake up during the night for some milk, but she may not.
And remember that 'sleeping through' is actually a solid 5 hour block of sleep. So if you look at it like that, she is sleeping through Sleeping for 7-8 hours overnight is a really good stretch.