believe it or not, I think this is common. My babysitters can put my kids down to sleep easily, but I have to stay in the room, lie with them (I always co-sleep - lie with them till they conk out and then I get up), rub their backs, stay with them till they are asleep. This was my choice from the beginning as I think it's good for them to feel safe at night.
But with the sitter or my husband, it's a piece of cake. They don't have to stay in the room as long.
I think with you * mom * she is expecting more affection, attention, and interaction.
Another thing is (I've noticed this with myself) if I was irritated and stressed and anxious for my then 5 yr old to get to sleep, I wasn't relaxed and HE couldn't relax. He picked up on my anger and that kept him up.
So you need to mirror what you want: calm, relaxed energy. Sleepy, end of the day, energy. Try not to watch the clock too much and just trust she conks out. Maybe it will take 13 minutes instead of 10.
When I worked myself, I was ENSURING it would take another 1.5 hours, until I realized my role in this. Good luck!