Why The Walking Dead Changed Alpha's Origin
AMC's The Walking Dead isn't exactly changing Alpha's origin, but the additional material shown in The Walking Dead season 9 episode 10, "Omega", does create a different impression of the character. The Walking Dead TV show's Alpha is a far worse person, shown to have always acted callously towards her daughter and be downright evil when it comes to anyone else. And while such cruel behavior may seem like an obvious character trait for a villain, there may actually be another reason why the TV show is choosing to include this an enlightening backstory.
In The Walking Dead comics, when Lydia is captured and taken to Hilltop, she doesn't act as outwardly hostile as Lydia does on the TV show. She's frightened, sure, but as for her opinion of the Whisperers, Lydia isn't as committed to their way of life as she is on the TV show. Instead, Lydia has a very good reason for not wanting to return to the Whisperers - they raped her, and more than once. In Whisperer society, the strong take what they want and the weak are left to defend themselves, so rape is considered to be a part of the natural order. Alpha lets this happen - even to her own daughter - and it's a convincing reason to vilify not just Alpha but all of the Whisperers.
The Walking Dead series, however, isn't likely to include a plot in where a teenage girl is raped, and so the motivation for Lydia to turn her back on the Whisperers is different. Not to mention, The Walking Dead has a better (though by no means perfect) track record at limiting its depiction of sexual violence, and especially when it isn't necessary to the plot. And so, while the Alpha in the comics isn't a very good mother (or person, for that matter), the Alpha in The Walking Dead TV show is shown to be irrefutably awful and brutal in other ways - which is more than enough reason to fear and hate her.
What It Means For The Whisperers
With AMC's The Walking Dead choosing to characterize their Alpha as being a cruel, overbearing woman right the get-go, it's possible this may also alter how most of the Whisperers come across. In the comics, Beta, her second-in-command, is absolutely devoted to (and clearly in love with) Alpha, and it's even implied that the only reason Alpha hasn't been overthrown by someone bigger and stronger is because Beta protects her. However, with how The Walking Dead TV show is characterizing their Alpha, Beta's devotion might stem more out of fear than of love. This Alpha is a terrifying and intimidating woman, and while perhaps that's what Beta is in to, it could just as easily be out of fear for their lives that him and the rest of the Whisperers obey her.
Just how The Walking Dead season 9 decides to develop Alpha's character following her introduction in "Omega" remains to be seen, but the foundation set for her has already made notable changes from the comics which portray her in a far more cruel and brutal light. Perhaps this is to avoid the rape plotline from The Walking Dead comics (only time will tell if the TV show chooses to include it) or because there was a desire to one-up their last major villain, Negan, with a character that comes off as even worse. No matter the reason, Alpha is already on her way to being one of the most vile and indefensible villains The Walking Dead has featured yet - and she's only just getting started.
The Walking Dead season 9 airs Sundays on AMC.