Sleep regression

So my LO is almost 15 months now and used to sleep like a champ! She would take two good naps during the day and sleep 12 hours at night. We used to lay her in her crib awake and she would fall asleep and wake up cheerful. Over the past week she has been screaming when we put her in her crib, fighting all sleep. The only way she will fall asleep is if we sit or stand next to her crib until she falls asleep. I need help and encouragement in what to do! Or at least tell me it will get better!!