I believe the packs of frozen mince you can get in PAH have some bone content if you don't want to feed bones. The other thing is that if you feed chicken wings, you could actually hold onto one end of them (possibly with pliers as it's a bit grim otherwise) while she starts on the other end of them, which might help with the guarding issue as you're obviously not trying to take it away from her if you're feeding it.
Zorro was very guardy over his chicken wings to start with (at 11 weeks old) so we hand fed them for a while, and also would just throw a handful of treats near him as we walked past, and then gradually just started standing a bit nearer (still giving treats) and these days he's fine with us humans being close by while he eats. He still growls at the cats though...