You could try making positive comments about your mother-in-law's parenting techniques with your husband. Once she hears you saying stuff about what you think she did great, she might be more open to acknowleging that you're doing stuff a little different and that's okay.
This helped my relationship with my mother-in-law quite a bit.
When she says stuff like, "give the baby juice" or "put rice in her milk", you could follow up with...
"It's interesting how different the recommendations are now than they were 25 years ago, huh?!?"
This takes the pressure off her to be right. She WAS right, based on what MDs were telling our moms back then.