How do I remove a contact from my zoho mail

How do I remove a contact from my zoho mail

I have a person that I do not know but I did give her my zoho email address. Now she is sending me information to promote her business 3 times a day. I'm not really sure if she is on my contact list. When I go click "contacts" I get stuff from my yahoo account and it's very confusing.

I just want to block her.  Can you please tell me how?