If the reader has one or only a handful of repeat clients copy-pasting the same or similar review every time without sharing any specifics e.g. "Thanks, great reading, try her, the best, she gave me hope blah blah" then yes it's a red flag. Sometimes, the person may be deluded or desperate and keep coming back holding on to the false hope that the reader gave them but in either case, this is not a genuine review and reflection of a reader's true ability.
You'll know the reviews are more likely to be legit, if multiple people are coming back and sharing specifics and if their predictions came to pass and each review is different every time. If someone is genuinely impressed every time, they will most likely share more about their reading and experience or predictions, not leave a generic thank you or one-line review.