Some "boy cut" or bicycle-short style cheer underwear has the opposite problem of the bloomers - that is, the squared-off legs show under the hem of skirt, which again can be a bit of a stylistic blunder in terms of cheer.
Whether called "bloomers," "Spankies," or "dance pants," there is a particular style of undergarment that is produced to complement the uniform - coming in matching colors and usually accompanying the basic uniform.
The primary way to deal with this is through attitude - cheerleaders wear Spankies or bloomers which are completely presentable and go at their routines with all the enthusiasm and spirit they can muster.
Still others are excited to finally enter the realm of womanhood, especially those who were late bloomers and were still wearing undershirts while all the other girls around them were wearing bras.
For example, if the problem is the bloomers peeking over the waistband, there are items like the V-front boy shorts, which dip down under the navel while still giving full coverage in back.