Want your 12 year old daughter not to have sex, then be an active parent.
Spend time with her.
Sign her up for after school/weekend activities.
Monitor/limit her social media use.
Talk to her about her feelings, and changing hormones/emotions.
Most importantly BE PRESENT.
Most kids having sex or unhealthy relationships at a young age, are only filling a void of neglect from their parents. If you are an active and attentive parent then your teen has no time or desire for sex or other unhealthy relationships.