Answer: Undue influence.
Explanation:
According to the situation mentioned in the question, Gene is convincing Hazel for agreeing to invest in the social networking site that is non-existent as she is her client.
It can be clearly seen that Hazel is not getting convinced due to her will rather Gene is taking advantage of her position of being her accountant and influencing her to invest in website. Thus ,Hazel in persuaded form agree to Gene's offer under influence.