Listen man, I would do both. You need a place where people an drop in and you cut their hair if you can afford a small place, you should consider doing it.
The mobile part you can always do when the client cannot come to the shop. Ever since they came out with the clippers and hair cutting tools made for the house, it really tool alot of business from barber shops. Sort of like what the internet did to big retail but on a smaller scale.
I`m not sure how big of a market it is going to people house to cut their hair. But you know the business and I`m sure you know more than me.
I agree with both gentlemen. Social network sites are good for brand awareness but will not pay the bill. the quality of the traffic is poor and will not convert well but as a viral/brand awareness tool they are great, especially twitter
If its not food or beverage related you dont need any certification or license to conduct business in the US. Depending on how you setup the business, the best advice will be to register your business for tax purposes.
In all honesty you are just being irrational to a certain degree. First off you told her the idea and it`s not like you can patent something such as a food idea due to the nature of it.
Why not just go into a joint venture with her? approach her about it and do business together or like you said just start your own and do it better than her. Sometime it`s more about the marketing than the food that makes you stand apart from your competitioin.