$2K for a woman and child is more than enough in BA (especially since you are going to pay school as well). That’s around $600K pesos. 100K for a good 1 BR apartment. 130K if the kid needs a bedroom. I can’t imagine spending more than another 150K-200K on food and household supplies. Chalk up another 50K for obra social and misc expenses. That leaves at least ~200K in what I would consider disposable income. And believe me, my calculations are quite generous. I’m assuming she is going to be living in a quite nice place (though not extravagant), buying all the meat and good quality food the two can eat (cooking at home mostly).
Obviously that is all dependent on her exchanging at the blue rate or WU rate.
My advice would be agree to it with the condition she signs something saying she won’t ask for more per month in the future. A kind of “I’ll give you everything you asked for, but this is the upper limit permanently”. Maybe you can leave a carve out for if the kid needs something like medical treatment or something expensive like that.
Just my two cents though. If you can work something like that then to me it’s worth not ever having to spend time in this pueblo again.