She may not be a bold faced liar, exactly. Splice may look enough like her kitty (Merle?) that she just told herself that he'd changed during the time he'd been gone. Or that her memory was playing tricks on her. Or something.

I do like to believe the best of people...

I'm glad you might get a chance to see them again. It might give you some peace of mind to determine that they're going to be a good family for Splice...or, if they give you any reason to believe they won't be, you can give all the evidence that you have that Splice isn't Merle, and take your cat back!

I'm sorry this has been such a rough experience. I hope, if Splice ends up staying with his new family, that another stray that needs you finds you quickly!