K.M.
My lifesaver was the book "No-Cry Sleep Solution" by Elizabeth Pantley. It took about 2 weeks, but I saw a HUGE improvement in my kids. Anytime I "fall off the wagon" and become inconsistent with the bedtime deal, my kids regress. Each time, I go back to her book and they are back on track within about a week. (They are 4 and 2 now.)
As for the cereal thing -- I know some people swear by it, but all 3 pediatricians I've used have said no way to that. If she's like my kids, she's probably not hungry but having trouble with fully waking up each time she enters that "light sleep" phase. It's the same phase where we grown ups roll over, look at the clock, and go back to sleep. She's just not going back to sleep. You can help her with that without going through the agony of "cry it out."
Also, with time, she may sleep longer, too. While 3 months seems like an eternity when you're sleep deprived, she's still very young. Things will improve.