Holmes will have to go and be replaced by a perceived 'grown-up' CEO. That's the only way (and even that is a longshot) the company ever recovers.
[1] http://www.forbes.com/sites/petercohan/2015/11/03/theranos-l...
Maybe she will run for president in a few years. She certainly has what it takes for a successful political career.
Investors agree to this for a few reasons. Firstly, it's a way for them to get a larger stake in the company. Secondly, it reduces the risk of the founders taking an early exit because they are strapped for cash. Finally, in a competitive deal (against other investors) it can be a way to sweeten the deal and get selected over the competition.
Investors don't want founders to be worrying about money - they want them to be focusing on their company.