Advice please - foaming dog, seperation issues

We have this great retriever mix, Naicha (who’s STILL looking for a home, nudge) and she’s absolutely perfect in every way but this,

our “other” dog (also looking for a home) was staying in the house while we were gone, until she started chewing on bigger expensive things, so…when we saved the second one, we put them both on our balcony while at school. It’s about 3 feet by 10 feet (not including the L shape). When we put them out there, Naicha starts scratching incessantly on the door, and starts foaming at the mouth…and continues, the foaming part anyway, until, when we get home at night, she’s soaked, from her mouth down to her toes, her whole chest, legs, everything. Not to mention I noticed, that being soaked in her saliva all day is making her scratch the wet area…

I have no idea what to do …it’s obviously her way of dealing with either a) the seperation or b) being confined to an area…or maybe both. But, is there something I can do?

Otherwise, this dog is the epitome of Zen…no joke