This whole exchange was documented by a Let's Date user on her tumblr.
She summed up the whole incident as: "don’t sexually harass a girl when she can easily find you on Facebook and send your mom proof of your perpetuation of rape culture."
According to a later post on her blog, she did, in fact, send the guy's nude photo to his mom.
She's received a bit of anonymous hate on Tumblr for it, but for the most part her followers have been pretty supportive.
Let's Date is an iPhone app developed by the the co-creator of alt-porn site Suicide Girls as a less anonymous, more accountable alternative to apps like Tinder.