3 year old won't sleep

Previous to the past week or so she has slept in her room and fallen asleep no problem and stayed asleep all night - now when we put her bed with her tv on she goes up fine and wants to go up then 20 mins later screams the entire house down and refuses to go to sleep without me or my husband with her or either wants to sleep in our bed - she's screaming and coughing that much sometimes we are scared of her becoming ill because of it because she sometimes throws up the more she screams - we are at a total loss of what to do now as everything we tried to get her to fall asleep on her own just isn't working we've even tried to bribe her and says if she sleeps in her bed tonight we will get her a toy - she did it for the first time when we said that and she got a doll house the next day - now she just says I've got enough toys downstairs now thankyou so not interested - anyone else gone through this and any advice or help please