My DD4 taught herself to read using starfall at 2/3 as well. She was like your daughter, she would want to sit at the computer for hours and it was a battle to get her away from it. She also didn't want my help, as with most things. So I had no hand in her learning any of the sounds. She was not a fan of flash cards either.
She was very big on environmental print (labels/signage/letterhead) and would point out every sign word she knew. If your DD likes games you can make it into a game. Ask her which sound she's learned and then tell her to let you know anytime she comes across a word that begins with T or that sound during the day. That way she's in control of it. My DD likes tests and quizzes so when we went to the grocery store we'd ask her to find 5 R's. She'd find them and ask for another task. We also had a set of sight readers. At first she "read" them to us by interpreting the pictures. Shortly after she had them all memorized by herself and then she began reading them on her own.
So, Starfall really works and if she's interested in it I'd let her do it with a reasonable limit as PP mentioned. Other then asking her what she learned and asking her to demonstrate that we didn't have to do any formal teaching of how to read.
