That's really sad.
I mean, here's the thing... I do get a little frustrated sometimes when training. Fortunately, in our class Kili is right on par with the other dogs which is very uplifting. I am so proud of her, but we absolutely struggle with certain things that come more easily to other breeds. And yes, it is a little MORE frustrating if she struggles with something because I did get her specifically with agility in mind and trialing in mind. BUT!
Big but. If I only wanted an agility dog I would have gotten a border collie. A border collie is absolutely, 100% a better suited breed to the sport. But I didn't want a border collie. I wanted a greyhound for numerous personal, non-sporting reasons. AND I wanted to do agility. When I get a little frustrated I try to really remind myself of that. She is a pet first and foremost and an agility partner second.
Sounds like this person should have been more honest about what they wanted a dog for and chosen accordingly. If she really just wants an agility dog she probably should have chosen a BC to begin with. If there was some reason why she chose this other breed then she should be more patient, have more realistic expectations, and stick it out.