I believe in child-lead parenting at this age. She's only 3 months old. She should be able to eat when she's hungry, sleep when she's tried. That's just my opinion. I definitely let them set their own schedule at this age, even if it changes daily or every few days. A 3 month old is way different than putting a 3 year old on a schedule.
Also, look for signs of when she's getting sleepy... instead of letting her get over tired. It's much harder to get a baby to sleep when they're overly tired.