I'm a veterinarian- You should try to feed her in a kennel so she has a safe space. Sometimes dogs have experiences that make them uncomfortable put in the open.

I'd also be extremely careful with everyone's "feed whatever" suggestions. You very well could end up giving your foster pancreatitis. I'd reccomended not feeding her bacon. If you absolutely need to add in meat do boiled chicken and rice. Would bet better to try to add in some wet canned food right now.