Did anyone try to check the grandmother’s signature ?
Why would you even bother after you know it's fake, and what it's been faked from? That's like wanting to double-check the signature on a supposed Andy Warhol portrait of Justin Bieber. The picture's a fake; there's no way the signature can make it real again.
The original image was only posted online four months before she died, and the blanked-out version was posted online AFTER she died.
Heck, let's remove the chronology for a moment. Why should the signature be checked? What's your hypothesis as to why a potentially real grandma's signature would be on a black-and-white, low-resolution birth certificate forged from that blogger's color, higher-resolution birth certificate?