help me! what do you ladies think?

Crae
I am concerned my daughter isn't nursing long enough. But I'm asking you to maybe get some peace of mind. 
   When she goes 3 hours between feeds she will nurse for 12-15 Minutes on one breast and then doesn't want the other. If she wants fed at an hour between feeding she will only go 7-10 minutes on one breast. Does this sound like she's nursing enough? 
She's having enough wet/dirty diapers.
 I just feel like she should be nursing longer. Let me know what you think. Thank you!