Two or more sentences may be best.
The witch struck. While binding Frank, at the same time, she snatched Bob away.
But the confusion isn't just in the sentence structure. It's also in the sense of the wording itself.
Can you bind and snatch simultaneously? I would put it to you that these are rather different actions, and probably can't happen at the same time unless either the witch is fast and
ambidextrous, or has four arms. If magic is the reason, then it's kind of a hand wave here.
I think a reader would find it confusing, too, because your reader probably doesn't know where the put their focus. Which is more important: putting Frank out of commission, or grabbing Bob?
The witch has to buy some time, because she (I am using this pronoun but if another is more accurate then of course by all means use it) has to:
- Produce ropes or handcuffs or whatever to bind Frank
- Then bind Frank and
- Pull Bob from Frank
I doubt Bob or Frank are going willingly.
So, the witch needs to buy some time, even if it's just a few seconds. What if she collides with Frank, causing Frank to lose his grip on Bob. The witch, thinking quickly, tosses Bob in the air. As Bob is falling, the witch binds Frank. Bob falls into her waiting arms and she spirits him away.
Or, in the alternative, she can hit Frank with her broomstick or another heavy object, thereby causing Frank to pass out. She grabs hold of Bob and, with her free hand, binds Frank. Then she escapes, with Bob as her hostage.
I realize these are both wordier but I think they make more sense logistically. There's suspension of disbelief, and then there's hand waving. Once the former crosses over to the latter, it is very, very hard to get it back.