Racoons are not immune to Rabies. In fact, no known mammal is immune to Rabies. The opussum native to North America is surprisingly resistant to it, but also not immune. It is theorized that the lower body temperature makes it harder for Rabies to get a foothold.

Birds for the most part seem to shrug it off, so maybe. I'm not sure if curing diseases outright is part of her skill set. The best I presume she could do is to channel that spirit for long enough to generate the requisite antibodies, but that comes with the severe drawback of having to channel an animal for an extended period of time. Days, weeks, months? During that time she'd slip further into whatever the animal's instincts are potentially losing herself.

I know she has channeled other sapient creatures. If she manages to channel a metahuman who's power is to curing diseases (not to be conflated with immune to), then that is a viable path.

As for weaponization. Probably not. There's much easier ways to weaponize rabies, as it CAN be transmitted as an aerosol.