What could be wrong with her ?

The day before yesterday Charlotte (15 months) woke up at 4.30am shrieking and I mean shrieking !! She was crying so much she was gagging and grabbing hold of me for dear life, I assumed she had a nightmare as once she calmed down she was fine again and was normal the rest of the day and the following night.

Then today again she has been fine, slept from 6pm to 7am no problems, brekkie no problems then suddenly at 12pm she just set off again shrieking like mad, grabbing on to me, gagging, etc ! I stripped her off (not that she was wearing much, just a body suit) and stood under the fan incase she was hot and she calmed down again & seemed fine again.

Now I know she is tired but she is refusing to sleep. She gets this sort of drunk thing going on when tired where she trips over her feet alot so I know she needs to sleep. Shes in bed with a fan blowing on her but not snoozing ! Now I dont know whether to leave her coz she'll fall asleep eventually or get her up but have her constantly tripping over herself as she's tired ?? Why is she suddenly shreiking like this aswell ?