Thanks @Rodney - This clarifies things even more and explains how the account ended up on Yahoo's mail servers. While I'd still recommend sunsetting the Verizon email account in favor of [perhaps] a native Yahoo account, it appears the Verizon Internet service can be cancelled immediately with...
If I'm understanding you correctly then the answer is "no," she will not. Yahoo, like most other Internet-based email providers, operates what is known in the business as a mail server. Since this particular mail server belongs to Yahoo, it's customers will usually have email addresses using...