Why would learning in Kollel be a “worthy tradeoff” to allow her to work if it is detrimental to her children, and forces her to compromise on tzniyus?
Talmud Torah K’Neged Kulam. Don’t you know the Gemorah that says a woman should sell herself in the Shuk so that her husband can learn Torah?
(I couldn’t find it either, but it seems to exist. Puk chazi mai amah devar).