Your questions had some good answers,and it is nice you had a talk and will try to find another way than using a chastity belt.
However,if you want to do this,you should never enforce it on her.You should convince her,the good way or the worse one.
The good one,is the one that Ivana(a Misterpoll poster)used:by wearing one herself and giving their daughters more privileges if they accept to wear one too(like later curfew)ans having fun talk,laughing,etc...together during the cleaning breaks.
The worse one is to threaten her;in your case,it is not by threat of stopping your financial help or breaking the relationship,but it can be a strict grounding,with no going out,no party,no friends,no cell,no computer use when not supervised,etc...until she accept to wear one.
Of course,I strongly advise you to use the good one,not the worse one(even if it is the worse one who is jused on me...).Maybe,after several talks,she understand she haven't behaved well and ask you to "help" her,with a chastity belt(but it is unlikely,I think).
If she hesitates,you may use it a bit differently:like Catherine,some "free days",without the belt on,while she's not allowed to have sex,but is allowed to relieve her urges alone(for Catherine,it is every other Sunday);or not plan to make her wear it until married, but until she dates an(approved,like after you had a talk with him and your daughter)boyfriend for long enough,and had good grades and behavior.
Of couse,if it is possible to solve the troubles without using chastity,it is even better.
