I can only wonder what people will make of BM's strength if this flashback was shown before we met BM herself (much like Kaido's intro.)
OT: While it's likely BM ate her family, it's possible CP0 had something to do with it. Why will she leave the clothes behind if she ate them, also, she's not that fast, they'll be able to run away from her (even if they don't successfully run away, the clothes will be at some distance from where they had the party).
Tho, I can't think of a suitable reason CP0 will leave BM behind if they were behind this event.