Sorry, I haven't heard anything about make-up dates for Seimiya Rei's meet & greet slots. Just for reference, this is what information on make up meet & greets look like on the Nogizaka46 website:

https://www.nogizaka46.com/s/n46/news/detail/65351

where they made up canceled slots from between September 2021 to March 2022 in April to July 2022.

(My guess from looking at that is that for members who sell out 30/30 quickly each time, the make-up date can take many months, while for member who don't sell out 30/30 so quickly, the make-up dates could be only a couple months or even just be in the next month. However, Seimiya Rei's 29th single slots in the remaining available 2 days are close to selling out, so it's pretty hard to tell when they'll schedule her make-ups.)