Jag försökte att ta min mammas kamera men hon ville inte ge den till mig, kanske eftersom hon var rädd att jag skulle brytförstöra den.

"bryta" suggests to me that something would be broken in the sense of being "snapped" (a branch, a bone in the body etc). Notably, this doesn't necessarily have negative connotations as it stands. If, on the other hand, you use "bryta sönder", then it is clear that the action resulted in (probably intentionally) the object being broken and unusable. Either way, the image I would have with "bryta [sönder]" and "kamera" would be you snapping it in half with your bare hands, which is probably not the case here.

"förstöra" is a very general word, and works fine here. It can also be used in the sense of "ruin" or "spoil".

"ha sönder" would also be fine here (i.e. "eftersom hon var rädd att jag skulle ha sönder den"). It's not very formal, which might work well here.

Jag vet inte varför jag minns det och jag är inte helt säkert på om det egentligen hände.