Even if you could believe there was an acceptable reason for taking home all those handover sheets and somehow keeping them - there isn’t, but if there was - that still doesn’t explain why one was kept in pristine condition in a keepsake box, or at her parents (where she didn’t live for any of her nursing career?) in a box marked keep.
A few scattered between the bottom of her handbag, car door, coat pocket you could put down to being a bit rubbish at remembering to follow strict patient confidentiality rules. But 257?

Nah, sorry. That’s 257 trophies.
She would not admit to having any sort of awareness of the handovers, despite having them under her bed, in different places and obviously taking them out of her pockets everyday to launder her uniform at which point she was aware. She said she didn't know how they ended up underneath the bed. I do think this was a calculated move on her part because if she had admitted awareness of them, then she would have been open for questioning about the organisation of them and how almost every single one in the charges came to be underneath her bed.
When Letby was arrested, she did not know which babies the medical experts would deem to be unexpected collapses. Yet, in the Morrisons bag she had handovers related to babies A-N, that's 13 babies.
She switched to the Ibiza bag after her holiday. So before the holiday, at that point in time, there was 14 babies that would later feature in the charges, (A-N) that's a very high correlation. Handovers for 13-14 babies.
She actually had handovers for every baby that she could at this point because there wasn't a handover featuring baby K.
6 of those babies never died, so what gave Letby the knowledge to have these handovers together at this time, when the babies collapses weren't considered suspicious until much later. These handovers are separate from the other 220-odd.
There was 31 handover notes in total underneath the bed, in the Morrisons bag.
She then had the handovers featuring babies O, P, and Q, In the Ibiza bag, which she used when she came "back with a bang"