My dd is a self-made vegetarian too!!! I grate cooked chicken and mix it into stuffing...she loves this!! Also ground turkey chopped up tiny into tomato sauce. She also loves my homemade chicken soup, as long as the chicken is tiny and almost un-noticeable.
You can sneak almost anything into tomato sauce!! Grating chicken is hard...sometimes I just chop it up tiny...like the size of rice.
Oh yeah, and recently I was able to hide some grated chicken into mashed potatoes...I'm going to try that with ground beef.
Good luck!!! IMO it's a good idea to keep offering the "real" meats, but keep on sneaking it in on the side. I offer it to dd every time me and dh are having it. Bless her, she will always taste it, but then spits it out!!