Not in the UK yet- Potential Harry Potter OC fic documenting trip?

Due to some unforeseen things (aka had to change plane tickets because extended Family stuff) I'm still not in the UK.
We leave instead next saturday- which is not bad and we'll be there by September 1st (and I'm going to convince my parents to go to the studio tour so that it can really be a HP centric day!)

and because of excitement to go to UKmy brain got invaded by a plotbunny to do a "dear diary" sort of fanfic from an OC perspective about "going to Hogwarts".

I'm already plotting it but I need a bit of help--

which would be more Canon-realistic premise for the OC beginning at Hogwarts?

A. Someone who got the original Hogwarts letter at 11, travelled with the Hogwarts Express, got to hogwarts, got sorted, but by end of week parents pulled her out because they "don't think she's ready for Hogwarts".  So she gets home-schooled (family full of ex-professors) and comes back for Third Year?

or

B. gone to different wizardry school and transfers to Hogwarts by third year? (the books/jkr? mentioned the possibility of transfer/exchange students (bill & the brazilian person?)- even if we never saw one in book canon.

I can go with either- but I want the one that would actually fit canon and not come across as rule-bending Mary Sue

so anyone can give me a hand with it? I sort of really want to write this and share it.