Keep in mind I am pretty new to the hobby of keeping frogs, but I always tell people never to mix, especially frogs that grow to different sizes such as Milks and Red Eyes. Milks get up to 4 inches long, and Red Eyes only two, I could see Orchid and her soon-to-be-bought playmate as parts of the menu for a few full grown Milks. I don't know if they have the same tendency as White's to eat anything smaller that moves, but with the examples of how they feed above, I could see it happening as an accident more than anything. Once one of my White's gets something in their mouths, they tear and tear at it until it can be swallowed (paper towels...>>).

But anyway, I agree with Tony, if you have to ask, you probably shouldn't. I don't plan on ever mixing species, though I do plan on getting an albino, regular and (maybe) xanthic red eye for one tank, and they will have no problems together. If they're not the same species, keep them separate, just to be safe.