have you tried giving half of what she usually eats? and then putting her back down for another 1.5 hours and feed again at 6:30 or 6:45?
at 7 weeks, she may be trying to drop one of her night feedings so she's pushing back that feeding to about 5. but i would go ahead and feed until she's ready to drop it all together. i remember my LO did that - ate at 2, then 3, then 4, etc. until she didn't need to eat at night anymore.
melissa