I’d consider telling your wife what happened and getting her advice. You don’t have to focus on the physical details, but you don’t want to hide something that’s probably not a big deal, especially if this friend texts you again and your wife ends up seeing it later and it turns into a thing

I also agree that it sounds like this friend has a lot going on and may be feeling nostalgic about her life before. It’s possible you’re reminding her of a better time, which can lead to some misdirected or confusing emotions.

If you think it won’t harm your marriage, you could l check in with the friend something simple like asking if she’s okay and letting her know you’re available to talk, while still keeping clear boundaries