The first line of the letter reads, "This letter is in response to your recent request to open a PayPal account. Our records show that you requested to open an account or make a purchase using the PayPal Credit payment method on 12/30/2017." She doesn't remember making any purchase. It occurs to me it could be a benign message due to a rabbit hole she backed out of on an online purchase. Does anyone have experience with this? Should I be freaked out? Thanks, reddit.
EDIT: Thanks for the advice. A little extra info, the letter is from Comenity Capital Bank (which appears to be a legit institution). My wife actually already has a PayPal account and it appears, this may, in fact, have been a phishing attempt. The letter doesn't ask for a response so I think the letter is legit. However, per the suggestions, we're checking her credit to get ahead of any issues.
Thanks again, everyone!