eea registration

i am married and i have my wife with me from pakistan she is currently on the 5 year route, also i get pip due to mental health illness, we are both self employed and we get tax credits, i also have a mistress who is in australia, and would like to come here to join me in the uk, she also has spanish nationality so from what i understand she can come to the uk, she would like to live with us in the same house, how do i go about doing things? she will also work with us in the business, can someone please advise