Yes, that is an older style of word usage from Jane Austen's time period.

for 是介词 ，这儿的意思是“为了…” （表示目的），按照正规英语语法， for 是介词 ，后面接动词时用动名词短语形式(for supplying her loss)，而for后面不能接不定式短语(for to supply her loss)，但是古代旧英语在当时可以那样使用。注意: to supply her loss是不定式短语，for to supply her loss = in order to supply her loss.