Christina keeps getting text messages from a number she doesn't recognize. And it's creepy. Leo says sometimes those messages are spoofed with a number id that doesn't exist and it's largely SPAM. Not much you can do but have your cellphone company block them. If it's the same number. If the number changes, it's a real problem to stop it. And if it's harassment, it may be a crime.
Probably the easiest thing to do would be to go to your cellphone carrier and have your number changed. If you don't want to do that, then there's not much you can do but ignore it. One thing you can maybe do is get a Google Voice number. Give that out, and she can have greater control over what comes to her.