Hi Mary,
Sorry to hear she is being a monkey!
A few things spring to mind, could be a growth spurt, Henry always tends to be a sod going to bed during a growth spurt, she could be ready for solids...therefore not full or satisfied when you put her to bed (don't know if you have weaned her yet?)
Alternatively, it could be a sign that you need to bring her bedtime forward a bit, perhaps she is getting a bit over tired and over stimulated...I know you've stuck to the same time for ages, but babies change, particularly as they become more interactive and busy in the day!