I wonder. Placement is KEY. We have so many coffee places to go for sure but when one is one the go, a drive thru is great.
Because there are already so many, the first key, I would think, is to be in a high traffic location that some other coffee experience hasn't already dominated.
THEN, she should do something that no other coffee stand is doing and BRAND HERSELF. IE. the cowgirls coffee stands are known for their super hot (and perhaps semi-clad) baristas. May not be everyone's cup of tea - or coffee, haha - but hey, don't you remember it? And I bet they get hell of tips there.
My fave stand closed and I don't know why. They were on my way to school at the time and had the best potato and egg breakfast burritos for only 1.50! Plus George and his wife were always full of smiles and happiness. I loved that.
So if one is going to go into coffee, better make sure you got a solid branding that will stand out. And make sure that location is hot too! (near bus stops, intersections, etc.)