That is EXTREMELY individual.
I dont know or see any around here, typical weights meaning 10-15 kg heavier than you (you are extremely light), except those who are over 90 kg (200 lbs), who uses a 16 m2 kite.
14 m2, occasionally a 15 especially for the heavy guys, is used for TT riding and necessary yes.
But we got all sorts of wind here, sometimes almost no wind, other times loads of wind, so would not make sense to have a 16 m2 that is "gutless" in every way, and get overpowered and pull you sideways if the wind picks up
Not many years ago, these sizes were used in summerdays - but now twintippers has found that a 12 or 14 m2 is way more fun and agile, and can almost start as early, so kites over 15 m2 are not really used here anymore.
Also, WHEN light wind, they dont go out but wait for windier days (not possible for you it seems), or, which happens more often, choose another type of board instead of a bigger kite - as this is a win win on days with changing winds where you just pick up the other board instead of rigging several kites.
(Assuming you are talking twintip boards, as if you rode on waveboards or hydrofoils you would not ask this question)
Some are fine with a light and really big kite, others hate these and would never own one, so as said - extremely individual.
If you trust your friend, meaning that you think you will have a similar liking - go for the 16 m2 is my advice
Nothing dangerous about this size, it has more grunt yes, and a fraction more power than a 12 but often not more powerspike, so TOO big, nope.
Simply personal preferences if you will like it or not...
With your low weight, you might consider the "light" big kites, as they can hang in lulls and be relaunched way better - where a "normal" 16 m2 kite, with your low weight thus relatively light wind even on a TT, will stay on the water unable to relaunch again if it goes down, and you have to swim or drift ashore.
Peter