It's wonderful if my sister has such a keen interest in starting her own pottery shop.A part of growing up is taking your own decisions and reaching out for what you want.But however, one who takes his/her own decision must also consider the consequences that the decision so taken would bring.Like they say, "A smart person always listens to all but does only what he believes in." I would definitely advice my sister to do a comprehensive research into the matter and also would advice her to first ask herself," Is this really the only thing that encourages her so much that she wants to make it her lifetime business." I mean, what if it's just a current fancy,that keeps you intrigued for a while and then you become bored with it.
But if she tells me that,"yeah...that's the thing I want to do exactly.", then I will simply support her and break the matter with my parents.I will try to change their perspective regarding pottery being not a "so-promising-career." I will encourage them to have faith in the choice made by their daughter and give their 'much appreciated' support." Though, there concern is also genuine but if a person is kept away from what he likes and want to do,he/she will never be able to excell in other things too.That is the thing I will make my parents understand.
Hope that's of some help. :)