It's legitimate - and your assessment (or hers) is correct - she tried to send a text to a landline. It's happened to me before, and this is how--when I pulled the contact name up to send a text message, it defaulted to the home phone, and I just sent it off, thinking (or not thinking, really) that it was going to the cell phone. When you are in your contact list, and editing a contact, one of the options for phone numbers is to set the phone # as default, either the home, cell or work. If you don't set one, it seems to randomly pick one, possibly the first one you entered for that contact.
Then, if you simply type in their name as a contact, to call or text, it pulls the default unless you specifically choose a different number. I'm willing to bet that's what happened!
Sorry, this is a different but related posting, and as I'm new to the community, I'm not sure I am doing this properly (sorry in advance for any breaking protocols).
I received this text as well with the same number (900080004222) as the source. Now every few hours I receive the same text reminder about the original call from a landline. As this is not a standard phone number, I can't opt to block it on the verizon webstie. I've texted "STOP" back to the number, but am still receiving these followup reminder texts at odd intervals. Any advice on how to stop this repeating text?