If you're planning to indefinitely cut contact with her, you should send it.
If you're still planning to maintain a relationship with her, then you should refrain and maybe think it through first at least.
I think deep down, your fear of her having a mental breakdown might be your fear of how this will manifest to more headaches and problems for you down the road. Although if you're cutting contact with her, then this is moot.
What goes up, will inevitably come back down. Whoever you have to step on when you go up, you will be at their mercy when you go down.
The truth is strictly what the ones in power perceives it to be.
Enjoy any good things, even the little and menial ones, as you will never know what impending distresses could descend upon you in a moment.