I honestly never connected with the "putting your characters through" this and that. All my characters have a story to tell. I take the role of an empathic writer who tells their stories in words on paper. I am senstitive to them, and I work hard to figure them out, their back story, their issues. Terrible things they go through are there because they bring them on themselves, with their behaviour and attitudes. I take no pleasure whatsoever in "putting them through" anything, I am just there to tell their story as accurately to their private experience as I can. I feel that forcing calamity on characters just to see "how they react" is unnecessary and a forced way to create a story. Besides, life is a thousand times more cruel, depraved, happy, magical, miraculous, than any of us could conjure up with out internal imaginations. I let the characters speak to me, because they are shadows of real people and real experiences that sprang to life to tell me something. So I listen.
As long as its adding to the character, taking her on a journey, crafting her into the character you want to be - I say go for as much as you want. I'm sure there is a line, but I can't think of one. Although, you do run the risk of depressing your reader to a point where they may not want to continue. That wouldn't happen to me, personally, but it might to some.
