Van helsings daughter (spoiler)

Maybe the Van Helsing gene only activate after puberty , that's why her daughter got turn .

Could be..after all her mother did have to hide her from the vampires

I don't know what is the science used by the writers here, but :

1) Remember that Dylan is the mixed offspring of someone already mixed.
Vanessa is part-vampire/part-Van Helsing. Dylan is part-human from her father but we didn't know which part she inherited from her mother. Maybe she didn't win the Van Helsing genetic lottery but got the vampiric side of her mother instead. What would make her part-human/part-vampire to begin with.
In these conditions, was Dylan "turned" by a bite or "activated" by drinking blood ?

2) We don't know anything about the Van Helsing lineage and how their abilities are passed down. Is each and every one of them gifted or is it 1 every 2 or 3 generations or more ?
I tend to think that it's a rare talent if not, vampires would be extinct already.

3) There's still another possibility... this is just a big misunderstanding 😂. The kid grew fond of Victorian clothes and has poor tastes in the makeup department. A cleansing lotion and some fashion tips is all Dylan needs.

I like your theory number 3 the best ???

I think her abilities are a by product of being a hybrid.

I think the Van Helsing's are just human.

I think Vanessa is simply an anomaly they're trying to solve.

Dylan being mostly human probably didn't inherit the anomaly.

I think Rebecca is her grandmother and this was her weird twisted way of rebuilding her family.