False optimist
Somebody that keeps trying to tell you it's all good between you and them (despite every indication to the contrary) or that you've forgiven and forgotten everything on their end, even though you're not forgiving or senile by nature.
The real cynics are the ones that seem to think everything is okay with everybody all the time, or that everything will be okay, so people shouldn't worry. That is false optimism, and people (a false optimist) who think that way are not good liars.
False optimist
People that are realistic about life might not make good liars either, but at least they don't put up a paper thin facade of being optimists where there is no good reason to be optimistic about something or someone.
A false optimist is the most negative kind of person around beneath the surface, but what's on the surface is everything to someone like that. What they have to show others for something is everything, even though it's phony.