Is there a way to get my 13 month old to sleep in later?

My doctor told me that my 13 month old's sleep habits are normal, so I'm not too worried about the amount of sleep, even though I feel like everyone else's children around me sleep a lot more than mine! She sleeps 9-10 hours at night and between 1-2 hours during the day. She has always been a bad/inconsistent sleeper, but what is getting me is when she wakes up at 5:30 am and cries until we come to get her. I have tried everything from putting her down later, making her nap time earlier, to making her dinners later, giving her more milk before bedtime, putting rice cereal in her nighttime bottle - but nothing seems to change her morning clock. Sometimes she doesn't even want the milk, she just wants to wake up and start her morning. Is there anything that can be done to get a baby to sleep just one hour longer?! The reason I don't want to just accept it is because every now and then she will wake up at 6:30 or 7:30 am! And I cling on to those moments hoping she can make it a habit :)