Hi dear, first of all, this will be a big change in your daughter's life so handle it in a normal way, explain to her about periods so that she's not overwhelmed when she gets periods. Tell her it's very normal to get it and it's not any disease. U can prepare a first period kit for her in which u can keep pads, few chocolates, hot water bag to help with the pain etc. Usually girls this young won't understand how to deal with stains so give her pads with wide back and wings to prevent stains as much as possible. Paree prima would be a good option, I use the same for my heavy flow days. All the best.