I've been searching for a word to mean a person who I know quite well, speak with but who hasn't been my friend. My friends are people I trust and can rely on, I have two or three of them. So, I found a word fellow which as I got it can mean it, but still not sure, and also all the examples show it's mostly referred to a male person. So the questions is: what's the most widely used word to call a person who I know but who's not my close friend? And can I say a sentence like:
Oh, I know Marry she's my fellow (she's not my colleague, let's say she's just my neighbor and we speak quite often)
Thanks.