Right, the Omega One are larger than other brand pellets...
When I had my adult boy, I used to feed him 3 Omega One pellets twice a day...
Obviously that amount was larger than his eye, be it 2d or 3d lol..but he never seemed plump or overfed...if anything he'd beg for more, but we know bettas are notorious for that! lol
But I agree, there's no set standard for amounts...and the description on the package should NEVER be followed. lol Anyone you ask will tell you something different...I've heard everything from as little as 1 to as many as 12 pellets or more a day. But the end of the day, pellet size and fish size has to be taken into consideration..
IMO the fish's belly should appear very slightly rounded after a feeding (but who knows, maybe someone will step in and say you shouldn't notice a difference at all lol) ... but if it noticeably balloons or always appears that way even between feedings...then the fish has definitely eaten too much and amounts should be cut back. :)
Also, be sure to allow her to fast one day a week to help clean out her system...:)
Maybe having a visual aid will help...:) http://www.bettatalk.com/food.htm