Hi there,
Typically, 12 hours is about the maximum a 6 month old will sleep at night. The average varies between 11-12 hours. So if you're baby is going to sleep at about the same time at night (6 pm), then I'd expect that she's more often than not going to be awake between 5-6 am.
If you are desiring a wake up time closer to 7 am, then you would need to work on shifting her entire schedule from wake ups, to nap times, to bedtime. And it would need to happen over a period of times.
It seems like the best plan of action would be to determine what "schedule" overall works best for her and for you. With some babies, you can work on setting a schedule that they'll stick to but keep in mind some babies have an internal clock of their own and so there may need to be some adjustments as she gives you indicators of when her body tells her to wake up and when she needs to nap.
Figure out when you'd like her to wake, when she might need to be napping and what a good bedtime for her will be. Then work on getting her on that schedule with regards to napping and bedtime.
Here's a link to some recommend schedules for a 6 month old:
http://www.babysleepsite.com/s…..-schedule/
You might also consider Nicole's e-book on Naps and Schedules as a way to help you decide how to determine the best schedule for your baby. You can find that at http://babynapswell.com
Keep us posted on how it's going.