Pacifier baby

Just keep it away and don’t give it to your baby. If she buys again, keep it away and don’t give it to your baby again. Do it until she understands. If I were you, I’ll just tell my MIL off nicely to stop buying. If she still buys, tell her off again. Keep doing so until she understands. Involve your husband as well. Keep all the pacifiers and eventually show it to her and tell her this is how much she has wasted money on until she fully understands.