She's dangerous in the same way Bernie Sanders was. However, I don't think she's infallible and has several weak points which can be exploited.
1. Outside of the vocal minority, I don't think most Democrats care about having a female president. They care more about other items affecting them than female equality.
2. Going off of point one, I think more Democrats would be far more easily swayed by an overt socialist like Sanders or a like-minded clone. People are losing ground economically, jobs are pathetic, wages flatlined. What is she going to do to woo these people? Which leads me to my third point.
3. If the DNC elite cozy up to her, they're going to have a tough time finding a platform for her to run on. Hope and change were ruined by Obama. If she tried to run on that, Trump would embarrass her on the debate stage. Unlike Obama's Republican rivals, Trump isn't afraid of playing dirty. Hillary ran on a dead end corporate/SJW warrior platform which Trump openly mocked. The DNC corporate backers won't let Oprah run on a socialist platform and if she did, the nominee process would lock her out for someone who is corporate friendly (just like Sanders). Much to the dismay of the SJW crowd who would probably call the DNC nominee process "sexist and racist"
The election showed us that people actually care about positions in rust belt states and don't care two shits about pointless social justice issues. Popular vote means diddly and I doubt she would secure the electoral college.
The Democrats are really in a pickle. Their corporate backers do not want an overt socialist at all, most of their constituents want Trotsky socialism, and the social justice animals continue to fall over themselves to drive away the more moderate voters. This coalition is fracturing under its own weight and I doubt they're going to be able to stay together much longer.
If Trump wants to seal the 2020 election, he needs to hit the Democrats where it hurts. If he were to get charges to stick on Hillary, Huma, Bill, and all of the other cronies it would utterly destroy the Democrats. This on top of the various voter fraud commissions that we keep hearing about make for any sort of long-term plan for the future difficult.
We still have the 2018 midterms which will be interesting. I doubt Trump is going to get anything done beyond the tax plan, but if he does that single bit above it won't matter. All he needs to do is tarnish and expose the DNC elite as the whores that they are and the party crumbles on its own.
Edit: Strangely enough, she's never married her lifelong "partner" even though they've been together for years. That's politically toxic in and of itself. She'll have to marry him. While Trump has had a litany of divorces, he's still "married" which is fine in the eyes of the public. Any political consultants will tell her to do this if she wants to make it in politics.