Clark is her cousin. If he wasn't mentioned or shown in some capacity you'd get the Avengers effect, where shit is happening and they go "lol why superman no help her".
I liked it, because if he didn't show up I'd have wondered where the hell he was too.
At least they explained it, and in a better way than any of the Marvel movies to date.
This is coming from a huge a Marvel fan and even bigger critic of DC.