H.T.
I would agree with several other moms in the suggestion of maybe trying club cheerleading. Clubs, dance studios and family athletic centers usually offer cheerleading and gymnastics and hip hop dance. Clubs usually do more competing than cheering for a particular sport. Also, go to some of the school games throughout the year and watch what the cheerleaders are doing (tumbling, dancing, cheering, jumps, partner stunts) then make sure these are some of the things she has exposure to at clubs or gymnastic classes. I would avoid the confrontation route of trying to figure out if the judging was "rigged". Unfortunately word will get around and you don't want the girls who did make the squad labeling your daughter as jealous or a spoil sport. You could talk to the coach and see if he/she has pointers, but make it casual and of an inquiring nature. You don't want to put them on a defense. Tell her she can still be friends with the cheerleaders. Don't be afraid to wish them "good luck at tonight's game". If she's sincere and friendly they'll start to know who she is. Cheerleading is a great deal about being outgoing.
Who knows maybe after being part of a club or dance she may want to stay there or tryout for the pom squad in high school. I cheered through Jr High and loved the dance part of it so instead was on the dance/pom squad in High School and at Purdue.
Just thoughts. Hope they help.