Hi A.!
You've already received several responses with advice that is very helpful. I did want to let you know that alot of the good advice, and the things I will say, come from the book "Healthy Sleep, Happy Child" by Dr. Marc Weissbluth. He is a pediatrician who has specialized in sleep research for infants through to adolescents for the past 25 years or so. His book has been incredibly helpful to me with my 5 month old daughter.
He recommends a couple of things in his book that may be helpful to you in your specific situation. I would recommend reading it, but since it's long I'll give you some short answers because we moms need that!
First of all, your daughter is sleeping right in the average of babies her age. The range of sleep in a 24 hour period for infants 0-11 months is 12-18 hours. Your daughter is right in the middle!
Second, Dr. W. says that the 3rd nap (if your baby takes it because not all do) should be dropped by 9 months at the latest because it begins interfering with bedtime. It may be time to drop the 3rd nap since she is going to bed later than before. One thing he says in his book that I've experienced first hand is that "sleep begets sleep" and "sleeplessness begets sleeplessness." She is going to bed later, but that does not mean she will sleep later. It actually has the opposite affect, which could be what is happening with your daughter. Dr. W. says that babies your daughter's age should be going to bed between 6 pm and 8 pm. The timing depends on how her naps were during the day, and when she woke from her last nap. My daughter goes to bed between 6 pm and 7 pm every night, and the variability is dependent on her nap schedule and tiredness level. You may find that putting your daughter down earlier will cause her to sleep longer.
Third, Dr. W. addresses sleep rhythms which means times when biologically it is better for them to sleep and when they should be awake. The first nap of the day should begin between 9 am and 10 am (depending on what time they wake up). The second nap should begin between 12 pm and 2 pm. (again variable based on the first nap). The third nap is variable, but it sounds like it may be time for your daughter to drop it.
Last, food is probably not what is making her wake up later. Someone else said that milk (breast or formula) is usually their primary source of nutrition until about 1 year of age. This is true. Do not worry about getting "enough" solid food in your daughter until your pediatrician tells you (i.e. either she is dropping in the growth charts or she is low in iron). Also, she will begin showing interest in eating more solids when she is ready. The milk they drink has significantly more calories in it than the solid foods they eat.
I hope this is helpful to you, and I hope I didn't give too much information! ;) Please let me know if you have any other clarifying questions. I am happy to help if I can!
God's Grace to you,
Lisa :)