Some acronyms are only widely known in certain places...like Joan said about OOAK, I know I didn't learn that one 'til I joined Etsy. A lot of forums use crazy acronyms that I never understand...I think DH means Dear Husband, right?
But as far as BFF goes, that one seems to get used EVERYwhere! It's been around long before the Internet was popular, so most people should know that one by now. I think you're safe!
I did take a look at the listing, and I like how you did it, with "best friend" in the title and BFF in the description. In the editing world, you always need to write out an acronym first with the abbreviation in parenthesis next to it, so people know what you're talking about. From then on you can use the acronym in the rest of the writing.