Absent friend

If your friend really wanted to she could and would say no to her daughter, especially as she is having treatment for cancer,maybe she complains about it to you rather than saying she prefers it to meet-ups.

It's up to your friend .
Nothing that you can do without upsetting her and making her feel pressurised to continue your social life .

Just be there for her when it goes pear shaped !

One of my friends did the same to me .
She used to be great company until her daughter demanded full time care at her house five days a week from 8.00 - 6.00 having driven
there .
The melting point came when the daughter wanted a third child .
Sadly , my friend became grumpy and morose .
I ceased to enjoy her company as I never knew when I'd be snapped at .

Just treasure the happy memories .

Live your best life but still have time for your friend when she needs you. As it is a newish situation probably best to let herset the pace. I find as I get older I am becoming more of an observer/enjoy the moment kind of person or else I would end up being offended over a lot of stuff. I just let it go and pop up positive.

cherish close friends.. she sounds like she needs some support from you...

Don’t lose touch, she clearly means something to you. Stay in touch via phone or messages and try and get a meet up, though not as frequently as you wish

How your friend chooses to spend her time is up to her. I can understand your disappointment but instead of being cross with her, if you think she’s so tired, could you suggest that you meet up and take the children to a park or something.
Schools will be going back soon and maybe she will have more time then.