I would introduce her with the other females. Size definitely doesn't matter. (Don't take that the wrong way), when it comes to a Betta Sorority. The alpha in my Sorority is the smallest and supposedly least aggressive one, and the biggest is on the bottom of the pecking order. Now she may be the Alpha, but once the other girls learn that she is, fighting should decrease.
A Sorority is really fun, but it is a lot of hard work. 2 of my girls died from the stress of being with the others, and now I have 5 in a 10 gallon who SEEM to be getting along well. Just try it out and see how it goes. If she's too aggressive, take her out. But as long as she isn't killing or severely injuring another girl, leave her in. It's a lot better then being with a Goldfish.