@christine_m, lots of comments above that all ring true. This issue came up early for me after my diagnosis. I did loose some 'friends'. Some said really stupid things to me and some are great. My true friends found it hard to watch me go through hard times. They didn't know what to say or do and many had so much of their own things happening in their life.
Covid hit as I was diagnosed and the isolation we all experienced compounded the whole situation for me. I let go of those people who were not good for me and accepted that even some good friends while they didn't cook meals etc, they were still my friends and great for a chat especially about non cancer stuff. We do need that break too. I used a counsellor for my thoughts and my medical team to help me emotionally process all the cancer stuff.
I am sorry about your partner, this is very hard and disappointing for you. You definitely would be hurt for sure about this. You are worth everything and don't need people in your life who can't be there for the hard times. Maybe a bit of counselling to help process that hurt would help.
Big hugs. You aren't alone here. Look at all the comments on this topic.