Is my budgie sick?

Question
Hi!
I have a 5 year old female budgie.  2 1/2 months ago she started to do weird
movements with her neck, it looks like really fast neck stretching.She's not
throwing up, it's more like she's trying to give food to something and I found
traces of food on her mirror and toys, it looks like a paste. If someone
interrupts her while she's doing that she'll stop, but I'm worried because she's
acting like that very often. I took her to an avian vet, they did tests on her
droppings and took a smear from her throat and didn't find anything. She's
eating and acting normally,her droppings are ok and her weight is fine (the
vet said she could even loose some weight) but I'm still a little paranoid
because she lost her mate 6 months ago (he had streptococcus) and her first
mate died 3 years ago from  megabacteria (they tested her for that too 3
times already,she's ok).  Something is wrong, but noone has any idea what!
Do you have an advice? Thank you!
PS: I hope I wrote everything ok, english is not my first language.

Answer
Hi, Morana.  Thanks for posting!

Thanks for providing so much detailed information.  It really helps in trying to answer questions.

I believe your bird is regurgitating to you.  Birds do this as a sign of affection/love for their human "mates."  This means your bird is bonded to you and considers you her mate.  This is perfectly normal.

Chrys