Mediators do not decide cases. If the other side is comfortable with the style of a particular mediator, that person may be a good choice. Call the proposed mediator (or better still, have a lawyer call for you) and inquire about what types of cases that mediator has done, how she conducts a mediation, and what references she can provide. Call some of the references and find out their opinion of how well the mediation was conducted. It is not a good idea to be suspicious of a mediator just because the other side recommended her. Most successful mediators do many cases with the same parties. It is not an indication of bias, but of trust.