I would request the review now, even after 3 months. You might have to explain how to do that. I had one very recent sitter who thought that she had left feedback for owners, but had only left responses to the owners’ review of her. I had to explain how to leave feedback. Even though her reviews as a sitter were all stellar, I told her that a lack of feedback from her to her prior HOs could be a red flag for future HOs. This is a younger person, so I would expect more technological sophistication, but it was obviously confusing to her.