I have heard that they shouldn't hold their own bottle and I believe that the reason is yes the bonding. Also, at this age your child should be drinking out of a cup whenever possible. It is easier to remove the bottle, pacifier, etc, when they are young like this, rather than when they are older and can ask for it by name. It is better for their teeth and jaw growth development not to have bottles, etc for longer than necessary. I would start her drinking from sippy cups with meals and snacks. Kids should never take bottles to bed, it causes tooth decay. I wouldn't remove the bottles all together but at 10.5 months, it should not be the main drink delivery system.
On the other side, remember that you are your child's parent, it is your choice, no matter what you decide, it will be right for your child. Maybe when sister says something, you could respond with "Thanks for the advice, I will keep that in mind." If she keeps it up then next time try, "You always have good ideas and advice, but I don't think that I want to change anything right now. I will look into it another time." Anyway, good luck.