Trump's attacks are entirely inappropriate. At the same time, this is a very left wing figure so what she says should also be taken in that context. It might be like getting Ted Cruz's take on an Obama era Texas disaster.
There was nothing "left wing" about her initial comments. She was merely responding to the present administration's statement that what was happening in Puerto Rico was "good news." She didn't even comment about Trump directly, but rather urged that the administration take better action rather than pushing a fake take on the humanitarian crisis on the island.
Trump, being his competent and mature self, saw this as an attack on his persona, so he decided to have an overnight Twitter tantrum, and that's how it started.
It would be nice if Trump could be the bigger person just once. But was there need for this mayor to use her own bully pulpit to rant on Trump?