Proxies are individuals who are under the influence of the Slenderman.
Or at least that's the technical definition. Tyrack is immune to such tricks, but she is more than happy to assist an... old comrade.
The relationship between Tyrack and the Slenderman is a strange thing. They don't necessarily need each other, as Tyrack exists on the Supernatural plane to keep the secrets of otherworldly folk and he obviously needs no help to keep safe... but they like to collaborate from time to time.
She is (or all purposes) a Proxy, but she is fully aware of what she is doing and makes conscience decisions while working for him. Sometimes she doesn't come home for months at a time, but this is usually for the best. As respectful as they are towards each other, Tyrack still doesn't trust him around her family.