Please help. Toddler will not sleep at night!!!?

My daughter is 2 years and 9 months. She has never been a great sleeper but latley it is getting worse. She wakes up at least 2-3 times in the middle of the night. She comes into our room and wants me to lay down next to her until she falls asleep. She screams and cries if I do not. I also have a 3 month old whose room is next to hers so I do not want her waking up the baby. We have a bed time routine. I have tried no naps during the day and taking naps. I have tried earlier bedtime and later bedtime. Nothing seems to matter. She wakes up almost every night. Any suggestions? Thanks