I think its important for you to know that graduate school in clinical psychology is extremely competitive. Many programs receive hundreds of applicants for a handful of spots. The people who get accepted are students who both excel in the area and have an obvious committment to the field. Now, I obviously don't know your situation, but given your other posts, please understand that psychology is not a backup plan for if dental school doesn't work out.
To answer your question, assuming you have a good GPA, I don't think a bio major will hurt you. If you can pick up a double major in psychology at this point, that may work to your advantage. However, most importantly, it is critical for you to get research/clinical experience. A competitive student typically has a high GPA (3.5 or higher) GRES (1250-1350 or higher), several years of undergrad research experience, and its becoming the norm for many students to take time off to devote to research for several years before applying to graduate school. Graduate school in clinical psychology is for the long haul. To be accepted, you need to show enthusiam, dedication, and motivation to the field. Not just for the admissions committee but for yourself too.
