Have you tried a central serving dish so that all the food comes from the same place but is served to her plate and to yours?
Mine had a phase of wanting my food or needing me to 'test' his food. I came to think of it as me acting as court jester, tasting the kings food to check for poison. In a way it sort of makes sense that they are safer if they know it is your food, it puts them at less risk of eating the wrong thing. However it's a PITA esp when you keep showing them it's all the same. I found this helped:
- serve the plates from a central dish
- put the food down in the same pattern (peas on right, carrots on left or whatever) on each plate so they look the same
- during serving name each food (even if they know what the food is and you know they can recognise it) as you put it on the plate
- after serving ask if LO would like you to test it for them, 'to check if it's good' take one piece eat it and say 'mmm, yep that's good to eat'.
- I also found it helped to chop foods in the same way for each meal so carrots always in batons rather than sometimes in rounds, sounds a bit silly but makes the item more familiar.
I wouldn't mind giving LO some off my plate, I wouldn't mind serving my plate then serving onto their plate, but I would draw the line at what you describe. Everyone needs a chance to enjoy their meal including you, there's a lot I'll share with DS but him spitting food onto my plate is a no go, ever. you could maybe try some of the above tips I found helped, if it's more extreme then I'd leave her plate almost empty, one small piece of food which she isn't going to eat, then when she wants yours pick up a piece eat half of it and put the other half on her plate. She has to take it from her plate to eat it.