[header] How to help prepare a preteen girl for puberty [title] Get her a training bra as soon as her breasts start to develop. [step] One of the most noticeable changes that may occur to girls during puberty is the growth of breast tissue. Explain to your child that this is normal, and that is happens differently for every girl. 
Take her shopping for a training bra when this development starts to help her feel comfortable about her changing body. [substeps] This change may start as young as 8 in some girls.