Speaking as a former 14 year old boy who went on all sorts of embarrassing shopping trips with my mother (and sometimes 4 younger sisters), I would say the reactions other people had were the least significant effect. The most significant effect is that as an adult, I'm can walk into the maxi pad section and find the ones that meet the required criteria. If I ever have a daughter I need to take bra shopping, I can handle that. Developing confidence and competence to do those things is way more important than the reactions of other people.
If a female founder conference helps women develop confidence or competence, or helps connect them to customers or investors or future employees, good for them. Those benefits will last a lot longer than whatever silly (over)reactions people have.