I went to a smoke shop & she wouldn’t sell to me b/c I’m 20. I told her there is grandfather clause. She still wouldn’t sell to me?

I went to a smoke shop. To buy a vape & some backwoods. 

She carded me right when I walked in the door. 

She told me “I’m sorry but you have to be 21 and up to buy any tobacco products I can’t discuss anything in the shop since you are under 21”

I told her that there is a grandfather clause that 18-20 before September 1, 2018 if you were that age before then you can still buy. She said “ive looked at that and it’s only Texas but it’s not nation wide and also on the FDA website they said it’s 21 and up and do not sell to people under 21 I’m have to ask you to leave”

We got into an argument and told her no it’s nationwide. And she said “no it’s not and also look at the FDA website I’m not selling to you & I’m not going to jail or getting fined and losing my job for selling to a minor. If you would like there is 2 detectives outside making sure I leave the shop safely that I can call them in here and they’ll tell you their self that it’s 21+ and nobody under 21 can purchase tobacco products so please leave”

She was rude and I contacted the bosses of the smoke shop and told them she’s rude and refused to sell to me and told them about it. And to fire her she’s not following the laws. And they said “it says 21 on the door and we can not sell to minors but you are banned from all 6 shops associated with ours that we run we watched the cameras while you guys are talking. For harassing her and trying to get her to do something she knows she would not do”

Am I wrong or right?