The thing NPD's fear the most is exposure, so when they feel like you are about to get close in exposing their larp they lose their shit
When that happens the first thing is turning it on you / gaslight / blame your paranoia
So the best way to deal with this behavior are two ways, the bad ass one, and the cringe one (the cringe one is more strategic)
Bad ass way: Keep gaslighting you fucking failure lmao "bye"
The cringe way: Pair their gaslighting, show patience, gather more info, and gaslight them instead
seriously tho
If you get in this situation without having the means to skip past their gaslighting with evidence, don't even try