For some reason the iCloud email linked to my Apple ID is someone else's who I don't actually speak to anymore. Is there a way I can create my own and link it to my Apple ID and remove hers?
An iCloud address is linked to a specific Apple ID and therefore nobody else could have set it up unless they had access to your account at some time. You cannot change your primary iCloud email address but you can add aliases.
Use email aliases on iCloud.com - https://support.apple.com/guide/icloud/use-email-aliases-mm6b1a490a/icloud - "An email alias is an email address that conceals your actual email address from a recipient. An alias can help you manage the email you receive, and monitor the sources of unwanted messages. You can both send and receive email from an email alias using Mail on iCloud.com.
I'm still not sure how I create a new iCloud email address though when this one is currently linked to my Apple ID?
Creating and adding new iCloud email and removing current one linked to Apple ID
