WordPress Admin Login Redirect

My admin login for WordPress is redirecting me to another site that I have to login. Here’s how I think my problem started: I have site A and site B. I used Filezilla to copy over all of the files from site A to site B so they would be the same. But now when I try to log into the admin panel for WordPress in site B it takes me to the login panel for site A. What could be wrong and how would you recommend that I fix it. Thank you so very much for your answers, I’m lost.