Cop Threatening More Charges If My Sister Gets A Lawyer

Long story short, my sister is dealing with a situation involving taking someone’s birthday bag from a local bar one night when she was pretty drunk. I was there, but was not involved. A cop informed her over the phone that if she decides to get a lawyer, he may “hang her out to dry”. He informs her that she’ll get a court date, be asked to pay the victim restitution, and the charge will be lowered to a ticket for disorderly conduct. He made a comment that my sister had to hand the restitution payment to a judge so he doesn’t get accused of keeping any… Then, the cop also proceeds to say that if she decides to get counsel, she better let him know as soon as possible so he can draft up the paper work to charge me as a co-conspirator and change her charges. Something doesn’t seem right with this situation. This was all over a phone call. What can I do? It’s not a requirement to inform them of obtaining legal representation, right?