My 3 and 1/2 yer old daughter won't eat much at...

My 3 and 1/2 yer old daughter won't eat much at all. Put a vegetable on her plate and the whole thing won't get touched. She has been like this for about a year and a half. She used to be this way about any food. I have tried EVERYTHING, I envolve selecting wthe foods we buy, preparing and cooking the foods but as soon as the foods are cooked she refuses to eat. She will eat breakfast and lunch but not dinner. I tried to tell her she had to eat her dinner or she could go to bed, so she choose to go to bed rather than eat her dinner, even at 5 oclock in the afternnon. I have tried to feed her 'dinner' at lunch time because I thought that she just might not be hungry i nthe evenings but had the same response. She will not eat sauce so I can't disguise the food with sauce. I am at my wits end. She is not lossing weight but is not gaining any weight either. She is in the bottom 5th percentile. (She has always been small but never this small) I know that this is a phase but how long will it last? I am a solo mum and always try to sit down with her a model eating dinner, almost every night we have dinner at the table without the TV on just talking about the day. I make the table a positive place, trying not to stress out or get up tight but nothing seems to work. I even tried to make the table look like a party, with balloons, and special party plates and presents etc, but she wouldn't have a bar of it. Ijust don't know what to do. Any ideas on other things I can try would be greatfully recieved. Thanks Desperate Mum