I believe that you should mention the racist comments. It doesn't have to be overly dramatic, but for many reasons, it is important to let the boss know that she is making you uncomfortable with her comments. I"d suggest language such as:
Supervisor, I need to share with you that coworker is making comments such as "fill in with a specific example" after she gets off the phone with some clients. Unfortunately, she is very loud and not only am I able to hear what she says, but some of our clients who have heard her have expressed to me that they are uncomfortable hearing these types of things. Thank you."
Don't offer solutions - not your job, that is the job of the supervisor. If the supervisor asks if the comments make you uncomfortable and if you want to file a complaint, that is up to you, but since they do make you uncomfortable, I'd strongly advise you to be honest with the supervisor.
Yes, people are allowed to have their opinions, but when they are sharing those opinions in such a manner in the work-place, different rules apply. It may be that you are not the first person to go to Management with this, it may be that Management doesn't care (in which case, honestly, I"d reconsider working for such a company, personally), but you need to let them know.