Don't break it entirely.  But fray it.  Disrupt it.  Make that bond technically there but useless.  You can do this.  We can do this.  We will do this.

"Oh shit um I'm helpiiiing!!"

Fortunately, you definitely don't become one of the world's top-tier superheros without developing good reflexes. Superman veers to intersect her wild, green-tinged arc, latching an arm around her waist to steady her.

"Ma'am, this is a delicate situation — can you help with the evacuation?" he asks, because telling rookie heroes to stop because they're not helping never works, and sometimes redirecting them out of the main battlezone does.

The nasty blue man is too hard to scratch. But the screamy green woman might not be. Teekl bats her in the face with a paw.

"Can't let this wait -" she grabs Teekl's swiping paw, and activates her magic-disruption spark, aiming at the rope of magic that stretches away from the evil cat, to someone else - "but I can't fight Klarion so yes I will go do that."

"Once we have hopefully made this familiar much worse at its job."

Teekl yowls, and contorts in the way that only a cat can, trying to pull her paw away.

... but she's still in Superman's grasp, and he was going to just take the cat far enough away to disrupt the ritual, but probably this works too.

He flies down to a roof, and wraps a bit of sheet metal torn from it around the cat at superspeed. Not tightly enough to hurt it, just enough that it won't be able to get away from the probably-helpful magician.

And then he leaves at speed to try punching the definitely-unhelpful magician in the face again. Maybe this time it will take.

Right.  Let's finish this.

The cat is tied up...  For the moment, she doesn't know if Superman knows just how good escape artists cats can be - anything that they can fit their collarbones through, they can fit through - and she has a grip on it sufficient to use her powers.  She is now going to try and break as much of the useful parts of the familiar bond, such as 'anchoring Klarion to this reality' and/or 'serving as a power tap', as she can, whilst still, hopefully, leaving the Witch Boy stuck with this cat and no other.  Avoiding the split worlds event will be much easier if she can just render Klarion moot now.  He had to anchor the thing on the young side of reality.

Visions of fanfic dance through her head - but even were she in the world of that one fic where all the available under-18s (across continuity lines) coordinated with eachother to pull off a proper reunification ritual, she'd still try to stop this right here and right now, because less potential mass casualty events is more gooder.

(Yes, she knows 'gooder' isn't a valid Scrabble word.  Blame the Internet for why she thought it anyway.)