I can speak spanish and arabic. I took spanish 1 and 2 in highschool and became fluent in the military. Arabic I learned on my own through 3 deployments to Iraq and Rosetta stone. I have huge amounts of training in Intelligence work through 5 years in the USMC. I also have a TS-SCI security clearence. My training cost the government over $250,000 (including all the investigations for the clearance). This all combined amounts to very little in the civilian job market. Anything outside of military contracting or a job with homeland security does not need my skill set. This is why I am continuing my education. My point is, your degree is going to be in Psychology, from an employment perspective which do you think will compliment the Psych degree best?
All I can really offer is to know what you want to do and take the minor that will best fit to exactly what your shooting for to make yourself the most marketable you possibly can. You need to be able to distinguish yourself from the other 50 applicants for a position.
In all honesty I don't know enough about Psych to offer educated input. If your not in a location where you will be counceling Spanish only speakers I don't see how a Spanish minor will be worth its weight. I don't see how biology would compliment it either but this is something you should look into. Maybe go and meet up with a Psychologist who does what you are wanting to do, buy him or her lunch and discuss it with them. Most professionals are more than willing to help out, especially if a free lunch is involved