I truly believe that weed is a gateway drug
You also mentioned her alcohol use; all the same correlations that support a pot "gateway" also support an alcohol "gateway" (ditto for tobacco).
and should never be legalized.
Its criminalization didn't keep it out of your daughter's hands. In fact, since well before any state had legalized pot, teens have reported that they could get it more easily than beer or cigarettes ... which is to be expected since legal sellers card and illegal sellers don't.
Without active efforts to keep it down, drug addiction will grow.
Its criminalization didn't keep it out of your daughter's hands.
No, because people like you continue to spread it. Some of it gets through the system and hurts those people with whom it makes contact.
Again, you are serving the forces of evil with your constant efforts to spread and enable more drug usage.