Dp and I split up a year ago. We have a 2yo ds. When we split we made a written arrangement, we agreed I'd have residence of ds but exP would have contact with him all day on a sunday, plus could see him/take him out during the week if he had time (he leads a chaotic life, works about 60 hours per week by choice etc.
We've been getting on well, trying to be amicable etc, until ex mil emailed me out of the blue today. It was a long and very patronising email, saying I need to make sure I always put ds first etc 
she said our arrangement doesnt suit her as she doesnt see ds enough. This is odd as I've never stopped her seeing ds, surely it's up to exP to arrange this? Her reason for suggesting Im causing her a problem is that she doesnt want to drive to visit ds, she wants him at her house, an hour away. Plus she thinks exP should have overnight stays with ds (exP hasn't asked for this)
She caused problems in exP and my relationship when we were together, publicly reminding of how he hadnt asked me to marry him, criticising my parenting etc. Today I visited exP with ds as he had a day off work, then I saw mil has bought exP a cot for ds even though neither of us have agreed to overnights and exP says hes happy not to until ds is older.
aibu to think mil should keep out of our arrangements and see ds when exP does?