id say confront her about the stealing first, cuz that shouldnt go down...
13 is kinda young and she is doing good in school id say just let her know that you dont approve of it, but as long as she doesnt do it all day every day and shit it should be ok... (of course if you dont want her to smoke then it would be different).. and maybe hide your weed tin beter... i dunno i hope some of this helped..