Awake time in the morning...?

Moriah

So my daughter is 7.5 months old, and can only stay awake for 1.5 hours when she wakes up in the mornings... This is right after 11-12 hours straight during the night, so shouldn't she be able to stay awake longer? I try to bump up time awake by 15 minutes, but she gets so cranky... Any advise?