Yes I believe that L'Wren Scott will be remembered for her fashion to those that she styled and worked with in her life maybe not to everyone in the world. I also believe that because Mick Jagger was such a popular celebrity at one time she will be also remembered as his girlfriend more to others.
Mick Jagger is not as popular as he used to be. L'Wren Scott on the other hand is a name unto herself. She will be remembered for her fashion rather than for her relationship to Mick Jagger, because she is very accomplished and well known for her contributions to the fashion industry.
Actually, many people had never heard of L'Wren Scott until the day of her death in which her connection to Mick Jagger was made apparent. He is a big name who has a big ego and many women understand how hard it would be to be connected with him so her name will always be linked with his.
As an American citizen in their 30's, I don't even know who L'Wren Scott is, so assuming she will be remembered is a misnomer. I am not a fan of fashion because it encourages people to spend money they don't have on items they could go without, so I don't even pay attention to that industry. A relationship with Mick Jagger isn't going to put a person on many radars either.