A. - I want to make sure I understand the situation. Are you saying that your baby sleeps for a total of 7-10 hours?
Every baby is different and their needs are different. I do agree that your baby seems to be getting less sleep than average babies. Here are a number of questions to consider before you can try to fix whatever might be an issue:
What does she do when she is awake - especially at night? Cry, Play, etc?
What time does she go to bed for the evening?
Is your bedtime routine consistent?
What is her disposition during the day too? Is she cranky, playful, etc.
I am sorry I am not more helpful but some of these questions are important to ask before understanding what may be going.
Maybe talk to your pediatrician. Or here some other resources for sleep related stuff:
Marc Weissbluth - Healthy Sleep Habits Happy Child
Elizabeth Pantley - No Cry Sleep Solution for babies
http://www.askdrsears.com/html/7/T070100.asp