I would be ticked ! Sorry but if you were enjoying eating at your favourite Chinese restaurant and then tried a new one and loved that one , would the owners be ok with you advertising for the other restaurant at their establishment ??
Just because she was so happy about Montessori , my thoughts are , who cares !
If she asked me I prob would of said um no !!
Regardless if she listened to me ( can not control her talking to the other parents ) I prob would move on without using her as a reference .
You mentioned she wasn't being mean , but she was being thoughtless .