I thought she came across great in the film though. Obviously they can't be honest before filming if they want to get genuine reactions etc. though I do think they should be honest about it after filming the scenes and ask the person if they still want to participate... even if it would mean re-filming with someone else if it's a no (or more likely, offering more money until they say yes).
I'm pretty sure it's usually how they get the "catfishes" to appear on Catfish. Just keep offering more cash until they say OK
.