So here I am. I didn't know what "SFM" meant. Thanks to the powers of Google... I do.
SFM means "So Freaking Much." (Or... "So Fucking Much.")
Here is the abbreviation, as used by a Young Person in the know:
i love dinner sfmYou would probably only used this generally, when expressing genuine affection. You would not use it as a means of dislike. For example, you'd only use SFM as seen above, and not, say, "I do not love watching Glee SFM." (Mostly because that's not how a person should speak anyway!)
— Kristen Yoonsoo Kim (@kristenyoonsoo) April 14, 2014
Gosh, it's hard keeping up with kids these days.