It´s a trap. She seems to suffer from an eating disorder, so if you directly respond to the statement, you can only lose. No matter what you say she will find a way to turn it around. Instead ignore the “I am fat” part and immediately steer away from the topic. Try something like:
I’m sorry, it looks like this is freaking you out. You know it’s not useful to talk about it, right? So, let’s do something to change the mood. Shall we (insert activity you both enjoy) instead?
It´s a trap. She seems to suffer from an eating disorder, so if you directly respond to the statement, you can only lose. No matter what you say she will find a way to turn it around. Instead ignore the “I am fat” part and immediately steer away from the topic. Try something like:
I wish you both all the best!