No offence hon, but you need to tell her that it is your decision NOT HERS!! There are so many benefits of breastfeeding that if you are happy doing it and not having problems then it's best for everyone to keep it up!
My mum and mother in law were both telling me that "theres nothing wrong with giving them a formula feed to make them sleep through" I just told them that I wanted to feed my baby how I wanted to...what do you know 4 months on and she is fully breast fed and sleeping through! No formula required!
It is so frustrating as the advice comes from the goodness of their hearts but you have to have faith in your ability to be a good mum and just let the unwanted advice go straight over your head! If you want to BF keep going and ignore them, it is best for baby anyway xx