I doubt there was any way she could have known that he'd actually win the nomination. So if she were involved it would have been a massive longshot that probably wouldn't have been worth getting involved in, considering the risk of being exposed as being behind it.
I don't think she imagined he would win. I think she just wanted to rile up the crazies of the republican base and hoped that Trump would take out a few more moderate candidates before he himself dropped out. She didn't need him to win the nomination. She just needed to make sure he did enough damage, took out a few moderates, and kept the Republican talking points unelectable. When Bush and then Carson and Ron Paul dropped out I think that was pretty much her end game. She was probably hoping Kasich would drop out before he did too, maybe at the hands of Trump. I don't think she imagined her plan would work anywhere near as well as it did. It has now worked TOO well, and he is probably panicking and so doing all he can to self destruct politically.
It really is a brilliant idea. Obama has been facing republicans doing all they can to oppose him for the sake of opposing him his whole time in office. Hillary saw that as an opportunity. The Republican base was simmering and nearly ready to self destruct the party out of mere tribal hatred of democrats (and minorities etc) and it was and is totally to Hillary's benefit to do whatever she can to push that over the edge: Enter her good friend, Donald Trump. Remember after Obama won last time and some Republicans were going around saying they need to reach out to minorities so they can win the next time around. That needed to be silenced or drowned out. And Trump was one way to do it. Republican talking points have been building towards this for a long time now, and Trump pushed it over the edge. He has a longstanding friendship with the Clintons and I think they urged him forward with it.