to be completely honest if someone sent me that message I would be utterly outraged. I understand the first part, but the second part about how she raises her kids is condescending and out of order. If she chooses to adhere to a strict routine with her kids this is her choice and her right. Who are you to say her kids are not better off with a routine?

If you choose to end this I would advise rewording the second paragraph to something along the lines of "I find it hard that I cannot see so much of you because of your kids routines, could we perhaps make arrangements so that we can all still see you without disrupting them? I respect your right to parent as you wish but sometimes I just miss you"
I agree. I really thing with the 2nd part you were overstepping the mark. I think what Traveller has said is a great way of getting it across.

Good luck with this and good on you for deciding to do something about your friendship