Your problem is not the choices she makes with her family, it's her constant going on about her financial hardship that those choices are causing. She goes on so much, to "shut her up" you pay for her when you meet up if I've read your posts correctly.
You are tired of listening to her over and over, and disagreeing with her choice makes it worse. Here's my take on both parts.
If the conversations is too much about money, change it. Talk about something else.
Meet in a park not in a cafe and bring your coffee from home so you don't feel pressured to pay for hers.
If she asks for advice, you can give some. This may or may not break the friendship. I've had some very tough advice from friends that I didn't want to hear and we are still friends. I have given advice in turn myself. But some friendships can't survive it. Be prepared for that.
You can ask if she wants advice., especially if you have tried to change the subject and she keeps circling back. Again, she may say she wants it, but be offended.
I would never say her choice of childcare is ridiculous, but discussing free playgroups, library programs to get socialisation without the cost, possible parttime work to offset fees are places I'd go. Ask her why she needs these two days childfree - she may be just struggling and desperately need a break. It might not seem that way from the outside but her mental health might be really fragile.
Sometimes, friendships arenn't really a positive in your life. Some friendships naturallly die. Whatever brought you together isn't really that deep a bond. If you can't talk to her about what you are venting here about, the constant repetative moaning about money that goes nowhere, every time you meet, then you really need to think about are you really friends.