A big question, then again, if she can pass the medical:
I don't see why Modi couldn't (unless he has some serious health issues we don't know about)
This isn't going to be a combat mission or even an aerial demonstration pulling 4G+, this will be a leisurely flight, a simple take off, fly about and landing. Modi has travelled by plane so this shouldn't be a huge difference.
In the IAF I AFAIK the requirement is for 20-20 unaided sight (so no glasses or contact lenses permitted) but other AFs allow for 20-20 corrected vision allowing for contact lenses and glasses, in fact many HMDS today allow for th option of the display retinal to be a prescription level so the helmet does the corrective vision for you.
+ I've said in the Rafale thread, this could be a big signal, IF Modi flies in the Rafale (a lot of reasons he won't- medical, safety concerns etc) this could be a clear signal the Rafale is coming to India.
Most MiG-21 and MiG-27s will be out of service by 2019 at the latest, a few MiG-21 Bison squadrons (the heavily upgraded version) will fly until 2022.
You realise he isn't gong to be flying a combat mission? He is only going up (potentially) for a joy ride, nothing more. He doesn't need to be a TACDE instructor to do that.
The AW-101 saga is not over, work is going on behind the scenes to get the AW-101s the IAF had originally selected as per the comments of the Indian Attorney General.