Oh no...poor little thing and poor you!!

Is she generally unwell, or is it because she doesn't want to be left alone?

You could try putting her cot at an angle by placing some books under one end of the cot legs, so she isn't lying completely flat.

Other than that, try not to stress. The monitor WAS on because you are an attentive mummy and DD is very lucky to have you. Also remember that babies and small children have excellent gag reflexes (much better than ours...I learnt it in First Aid). My DD used to spew on herself all the time as a small bub, and I would often pick her up and there would be vomit in her hair and on her bed and I hadn't even heard her spew!!!

Hugs to you...and I hope it resolves itself quickly.