Not quite correct.
While they are reimbursed for travel for which they pay for, which all presidential advisors are, they do not collect a salary/stipend, which most advisors are eligible for. Even Trump doesn't keep his salary, he donates it to charities.
Since they don't live in the WH, they do not live or eat on the taxpayers' dime, they pay their own living expenses just like all members of the President's staff does.
The other part that is incorrect is the Citizens United quip. The ruling stated that corporations and unions could use their first amendment right and their money to advertise a political view. They CAN NOT donate money to a candidate or political party directly nor can they mention a specific candidate in their advertising. I think it was a bad ruling, but it is what it is.
So the money that Maxine pays her daughter comes from donations directly to her campaign from the average person, not corporations or unions. I think $750k/yr. is a gross misuse of funds, it is immoral and unethical. That, however, is just my opinion.