This is what you get for being so internet-connected.
When Harley Quinn successfully escaped
from Joker (and managed to not get zombified herself), it didn't mean her troubles were over: this is Gotham City, after all, and Gotham is crawling with heroes. And the heroes retained enough of their intellect/personality to still act intelligently, which is why they were drawn by the sounds of gunfire; Harl shoots Mistah J with a shotgun, and she's barely turned around before she's confronted by the Zombie Birds of Prey: Catwoman, Huntress, Batwoman, and Batgirl.
They're not given any backstory, but Batgirl is one of the most terminally online heroes around, so we can extrapolate. The virus is whipping through the internet, so she sees it and is infected, then starts on the others. Huntress first, probably, or maybe Batwoman since she'd be the least likely to see it coming. In any case, Catwoman would have been last, since she doesn't nomrally hang out with that crowd. But she also works alone, so she didn't have anyone to save her from them (which is the main reason Harley didn't get roped into their impromptu undead team-up).
Batgirl is wearing her Burnside costume,
because that's what DC Essentials had already done (as figure #10). These figures all reuse existing bodies, so this Batgirl gets the same Sam Greenwell sculpt from 2019. Well, probably from 2018, but it was released in 2019. You know what we mean. Since all her parts are unique to her, she gets to be a little shorter than average - still over 6⅜", but that's short for this line.
Batgirl's head was sculpted by Paul Harding, like all the zombie heroes and villains. Her mouth is open to bite someone, there are scratches over her face, and her pupils are just pin pricks. There's even a little lock of hair poking out on top of her head, a good shorthand for "battle damage." For some reason, her cowl comes down over her jaw, instead of stopping at the cheeks like it's supposed to.
Other than the head, all the molds are reused,
which means no sculpted wounds. She gets the "clawing" hands all the zombies have had, but there are no rips in her costume - guess wearing a leather jacket instead os spandex was a smart choice! She does have plenty of blood, though: on her hands, her knees, her thigh, her arm, and all across her chest. She may not have any torn fabric, but there's no mistaking this for someone who's had an easy time of it. The blood manages to stand out even against the dark purple of her suit.
The DC Essentials line had quite good articulation, so DCeased Batgirl has a balljointed head, a hinged neck, a balljointed chest, swivel/hinge shoulders, swivel biceps, double-hinged elbows, swivel/hinge wrists, balljointed hips, swivel thighs, double-hinged knees, swivel shins, and swivel/hinge ankles. It's a bit weird that her shin joints are just right through the middle of the leg, rather than at the already available boots. Unlike the Mattel version of this costume, DCD's actually has the strap around her right thigh that's meant to hold her pouch in place (though they're not actually attached, so the joints can move freely). The original release included a batarang, but this one gets nothing.
When the DC Essentials DCeased figures were cancelled, Batgirl wasn't even a painted prototype yet, so she was the unlikeliest of the unlikely to ever see release. The toy could have been a lot better, but the fact she exists at all is impressive in its own right.