I can definitely understand having questions about messages you receive from Short Code numbers. These type of messages are typically connected to a business, or app that you may have used. If you did not recently use an app, or reach out to a business that send this to you, I would recommend ignoring the message.
Thank you for letting me know. Short Code is definitely used for verifcation services. This can be from any type of business, or app that she may be using such as a login to a bank account, or a credit card company. It can also be used by apps like Facebook, Twitter, or other social media as well.
Alrighty then. Is this random text causing any issues with the device itself? If not, she should be able to reply STOP to that short code to stop them from sending the texts in the future.