I love Hillary and I do think she would have made an extraordinary President, but I don't think she should. It's not worth it. She should enjoy retirement and enjoy being a grandmother.
Depends how big her popular vote lead is and how absolutely horrible Trump is. Some of those Rust Belt voters could have buyer's remorse and that alone might be enough to give it to her in a rematch.
I haven't see all the remaining outstanding vote totals, but California should easily take her to at least a 2% margin.