But you chose to accept that job. The actor on TV isn't being treated unfairly because he/she has to lie and say they're a detective, or whatever. I don't see why the model is being mistreated because her role is software company employee.

If anyone is being mistreated by the lie, it's the person being lied to, who is, you know, being lied to. That said, this is a balance between having a fun party, and possibly feeling dumb when it turns out the girl you thought you were flirting with is actually a model hired to entertain you. I think it's up to those companies, the employees, and the models, to strike the right balance.