MIL treating grandchildren differently and how to approach it

Hey everyone,I (34f) have two daughters (5 & 13) and one 2 year old nephew.Before my nephew was born my mil had a good relationship with both my daughters, she would help with childcare one or two days a week before they were in school, take them for the odd days out in the summer, would invite them to sleepover sometimes. Once my nephew was born this all stopped and I just don’t understand why. She has him overnight at least once a week, looks after him 3 days a week and talks about him all the time - whereas now with my daughters she only ever sees them when we take them to see her (prob twice a month), if we ask her to have them she’ll say she’s too busy, or they can’t stay overnight anymore because there’s no space (she’s has 2 spare bedrooms!).I just can’t understand the complete u-turn in the behaviour to our kids, and I don’t really know how I can bring it up with her without causing upset (she hates any type of confrontation and is quick to turn on the tears). I feel sad for my daughters because my eldest especially has picked up on this herself. Has anyone dealt with something like this before? How did you go about it? I’m getting to the point now where I feel like I’m holding it in whenever I’m around her and resent her for it! via /r/Parenting https://ift.tt/2PCr7St