Love her or hate her, but that's the truth.
There are some characters who may have very little screen time, but even so, they can immediately capture the viewer's attention and make the show their own. A good show is full of secondary characters like this: short-lived and not all that important in the long run, but very well thought out and impressive.
The Big Bang Theory was great not only because of its refreshing premise, but also because it never had a problem introducing secondary characters. Howard's mother, who never once appeared on the screen, is the best example. Stuart, the owner of the comic book store who ended up on the street, is another.
For the main character of the series, Sheldon Cooper, the most important secondary character was Meemaw. His grandmother, who, as the audience quickly learns, was always his favorite family member.
Although Meemaw, as portrayed by Annie Potts in the Young Sheldon prequel, quickly became a fan-favorite character and practically stole the show from the titular character himself, it wasn't the same for TBBT's Meemaw.
Judging by June Squibb's appearance, viewers expected to see a harmless old lady, but instead got a strong Southern woman with a lot of sass left in her. This made Meemaw so entertaining to watch, but it would also make her absolutely impossible to stand in real life.
Her obnoxiousness peaks in the episode "The Meemaw Materialization," where she visits Pasadena to check on Amy. You can say she's only motivated by love for her grandchild, but that doesn't excuse the rudeness to his loved ones. Especially when Sheldon himself says he's so happy he's ready to propose.
Of course, Meemaw is a woman who has had a hard life at times and is used to other times, but she seems to hold Penny and Amy to a double standard, practically saying that caring for Sheldon should be Amy's full-time job. For a neuroscientist who has been pursuing her career for many years, that remark alone would be extremely offensive.
Fortunately, Young Sheldon's Meemaw has changed just enough from the original character to still be herself, but not have such a double-edged effect on viewers. In fact, some believe that if Annie Potts had been playing Meemaw all along, Amy wouldn't have to defend herself in the first place.