if you older much older and you used to do brotherly , sister stuff when both of you were young, try to relive moments that bring a smile to both of your faces.
For example, if she used to love going to a certain Mcdonalds for icecream when she was younger, bring her back there, for ice cream. why you ask? because the way i start off a serious convo like is by usually flooding the other person with happy thoughts, just so she can remember what it used to be like and not be clouded on thoughts about the trouble you guys have.
start off with : hey you remember when we used to go to XXXXXX for XXXXX?
her : yea i remember that.
you : what ever happened to that ? i miss the good old days on how tight we used to be.
( at this point you drop all ego and let her have it )
now we're just bickering each other for stupid things. bla bla bla, go on with it.
All previous posts have valid points and good ideas, but the way i look at it, why wait for them to mature to fix something? You just have to remember, fixing something requires change from both parties. Whether it maybe her needing to open up more to you or you having to understanding something about her, just be aware of it.
i would give anything to fix anything with my younger bro. He past away when i was younger and i never got to say im sorry for all the things i did.
I hope this made sence guys. im writing this while trying to sort some paperwork and im writing to many run-ons