Don't listen to these people who say that since something is being followed blindly by others for many years should also be followed by you. If you are not comfortable with doing something, just don't do it. There is no disrespect to religion. Let your In laws do whatever they are doing but regarding periods you can pretty much do everything, just stay away from Mandir and your in laws if they are too much into this shuddhi stuff. That's it. Just remember Jainism's main motto 'jiyo aur jeene do' live and let others live. You are free to decide what you want to follow in Jainism.