I'm really glad to see you taking your life back, and overjoyed that you are sharing this with your SiL. I want to make sure you are aware that even if everything goes well, and it most likely will, the first few days to two weeks are going to be the toughest. Your brain is going to play games with you, it's going to tell you that you are starving, your going to have some seemingly impossible cravings. I have no doubt that you will get past this without much of a problem, but I want to caution you about leaning on your SiL too much at that time, if she decides to follow your lead, then she'll also need to know what to expect, but I feel it would be best addressed as hindsight rather than in the emotional state that may be going on while these feelings are happening. I hope you understand where I'm coming from here. I really want her to see the benefit of what this surgery can do, I fear that since you say she has "given up" she may view the short lived struggle as too much to deal with, and lose out on the new life this creates an opportunity for.
I don't wish other sleevers luck, as I believe it is not needed. But I'll wish you all the best with your new journey & your new life.