Re: advice
changes are a part of life, a suggestion i have if you can set aside some time for HER, talk to her on the phone, and when you do don't gush on and on abt your fiance, rather talk abt things that you guys would have normally talked abt before marriage, like movies music, tv shows, shopping. Make sure u give her time that is truly dedicated for her and let her know she can contact you anytime.
often the younger siblings feel like they are forgotten about especially at an upcoming shaadi, they feel that the older sib has abandoned them, and most of the younger sibs do in some way look up to the older ones. I guess the important thing is that make them feel like although you will be married (congrats btw) you will still be there for them.