A possibility was discussed in the last few threads that some of us did a test. I turned my phone into airplane mode and made a bunch of texts. Then I turned my phone off. Then I waited and turned my phone back on and it did not come back on in airplane mode. When it came backon it sent the text when I turned my phone back on. Darn it, I forget whether I had to log in for them to be sent, or they just went automatically when I turned the phone on but I had not logged in with password.
I guess I'll have to do another test later unless a kind person wants to do it for me before then LOL.
That is how it works with a Samsung Galaxy 7.
If it gets sent by merely turning it on, and without and putting a password, it is possible that some very conniving person could have given it to her and they were sent without her knowledge when the phone was turned on.