I must say, this isn't common and it for to continue happening for so long is super rare. I'm sure it's frustrating for not only your friend but also for you if you're trying to get a hold of her. It sounds like her number needs to be rebroadcasted. To get that taken care of, you'll need to contact Tech Support via 611. It's best if she calls on a different phone so that all troubleshooting can be completed. Give that a shot and keep me updated!
Have you reached out to our Tech Care team? Please keep us updated. Thanks!