I have had receptionist positions in the past and one of the things that got me hired in one job was when my prospective boss asked me how I viewed the position of receptionist. I felt that my behaviour and attitude toward clients reflected on the entire company, and that customers wanted a receptionist that was welcoming, courteous and professional, and that co-workers needed someone to ensure that that their messages came through correctly and legibly, and that they could trust that their customers would be treated in a way that would make them want to come back. I said it was like people arriving by boat to the USA for the first time and feeling inspired at the sight of the Statue of Liberty as opposed cringing as a garbage scow floated by.
I seriously don't like that she's flaunted her sexuality to you. That has absolutely no place on the job. Your company has a dress code, yet she feels that she doesn't have to abide by it, and it detracts from the professional image that the company wants to portray.
It's going to be tedious and time consuming for you, but you may need to start keeping a log documenting the dates and times and specifics of her inappropriate and unprofessional behaviour. You'll also have to watch your back and make sure you deal with her in an utterly professional manner, without making any reference at all to her sexual preferences or her weight issues (because if you do, those can result in discrimination suits).
It's really a shame that people in these positions are not required to take some kind of entry level training to know how to behave professionally. Sometimes I really think these kids have no clue how to behave on the job and think they can get by the same way they did through high school.
Love, Scully