As far as your mother is concerned, she is most likely just scared. I'm sure it's coming from a good place and not a matter of "to support or not support". My hunch is that even if you are overweight she may not "see it that way" BECAUSE you are her child.
If YOU believe that it's the right thing for you and your DOC feels it's the right thing for you, then that's all of the support you need.
Support is a great thing, and once you do it, support will be there by those closest to you and if it's not, you'll have to separate yourself from those people. The thing is, it has to be a "you" decision. YOU have to do this for YOURSELF. Sure the sleeve helps, but you NEED to have the motivation and will to see it through and make sure you stay with it moving forward.
Just like the lap-band, there will come a time where the "restriction" you feel in the beginning is not as much. You need to use the time that you have it wisely and make sure you develop good eating habits and exercise habits during that time-frame.
There are groups you can join if you need to talk or need support outside of your family/friends. Support is great when it's there, but you have to be prepared and motivated to do it without support if needed, because at the end of the day, this for YOU.