I know here in the states, you don't need to be helped by the same person I don't think. It's just a courteous thing to do I guess. If someone's been helping you the whole time and then it wouldn't be nice to then have someone else help you in the end to get credit for your purchase. I'm not sure how it works. I usually just go to my fav MA's and wait for them and kindly tell other people when they try to help me that I'm just waiting for [insert name here]. They seem to look disappointed since they know that I always go there and usually make big purchases lol. Anyway, there was this one time I just stopped by the mall because I really wanted some items and couldn't wait to contact my fav MA to ask when was the next time she worked. I had to have it NOW! lol. So one MA helped me get a Global Glow MSF. I said I wanted to look some more so she left me to continue doing a makeover. She told me that she was going to hold on to the MSF and to get her. When I was done looking and figured what I wanted, I wanted to come to her but I didn't want to interupt her while she was doing something with another customer. So there was this other MA who was doing absolutely nothing (This was near closing time so it wasn't busy in the least). So I asked her if she could help me (I really needed to go before the Sears entrance to the mall closed, or else I'd have to walk all the way around the mall from the outside
) So I had her help me with the rest and she grabbed the MSF from the other MA. She was yelling something to the other MA about something. I think maybe she gave credit of the MSF to her or something. I'm not sure how the whole thing works but yeah. I felt kind of bad about having another MA do my purchase but ... you gotta do what you gotta do!
That MA shouldn't have made you stick to her IMHO. Seems really rude. Now no one got any sales from you. As a customer, I think you have the right to choose which MA to help you! If you don't like them then you should be able to find someone else!
I'd say get the names of the MA's you like and whenever you go to MAC, and someone you don't like comes up to you, just tell them that you're there to see a certain MA (that's there of course lol). They shouldn't be pushy after that, or at least that's what I've experienced.