She largely defrauded idiots on the investor side, granted. But that's still not allowed. Even defrauding idiots is a crime.
[0] A professional investor is an individual or legal entity that possesses the experience, knowledge, and expertise necessary to make their own investment decisions and duly assess the risks associated with these decisions.
To be clear, most of the investors weren't VCs and things; they were, largely, individual rich idiots (or their family offices, at their direction). Theranos had trouble with real VCs, who wanted inconvenient things like audited accounts.
The rules protecting accredited investors are indeed laxer than those protecting normal people, but it is _still not legal to defraud them_.