Call me a heartless bitch, but I honestly think she doesn't care much about either of her kids, so they wouldn't be really good, as blackmail material.
I mean... she vlogs and does her make up while behind the wheel and with the kids in the car, completely uncaring of the fact that she could get into an accident and kill not only herself, but the kids too. As if this wasn't enough, she allows very young and (presumably) inexperienced girls she has met online to come to the McMansion to take care of the offsprings of the Onion so that she can film her awful make up tutorials and such. She wouldn't expose them to that dangerous and toxic enviroment at all, if she behaved and thought like the adult woman she is supposed to be.
:autism::autism

Not to mention that it was the Onion, the one who chose the names for both of the kids, and he named the boy after his favourite movie and the girl after one of his exes or sick shit like that.):autism::autism:
I'm not even really angry at Taylor: she was groomed at the age of 16, and since then Onion kept the enviroment around her as toxic and childish as possible so that he could have his child bride as long as her body stayed ripe and fresh. It's a normal thing, in victims of abusive relationship, to behave like they behaved while being groomed. It's normal for a 16 year old kid to not really care about children, to find them annoying and the like.
If she found the courage to run, she probably would grab some shirts, enough money to make it back to her parents, her phone and a pair of shoes. The kids would be left with the Onion Man, as they never seemed to be the priority nor something to protect, for her, and therefore are probably forgettable.