Should I add a note in my creative writing piece for my lecturer?

Basically, I am in my final year so I am trying my hardest to make sure I do not get marked down for an essay I am currently writing.
I am required to write 1500 words of the beginning of a creative fiction novel.
I am writing in the style of the 'unreliable narrator' in first-person and am trying to insinuate that the character slowly loses grip with reality throughout.
However, it's hard to make the reader realise this in just 1500 words.
I so far have written that the main character's friend has a deceased father ("He told us he used to go camping all the time in the forest with his father before he passed away"), but then I go on to mention a few hundred words later that
my character had to "convince Hassan’s parents to let us go camping."
I added this as the first reference of my character remembering things incorrectly, but I'm worried that my teacher will just think it is an error and mark me down for it.

Do you think it would be appropriate to add a footnote explaining this, or should I just hope she understands?
I do have an extra essay due which is Part 2 of the module which is about choosing a piece of work that had affected your writing style, and the book I chose has an unreliable narrator too, however, it is not about losing grip on reality like my main character.