I have one friend like this. I notice it usually coincides with an opinion I have that she doesn't agree with. For example, she firmly believes there is no racism in Britain and I posted an article written by black Britons about some of the systemic barriers they faced. After I posted that she went cold. She was cold for a few weeks, then fine again. Made an off the cuff comment about the article which confirmed by suspicions about why she went cold.
Weeks later after lots of normal friendship/banter etc, I then posted a really good info about health care for black Britons, followed by something shared by BLM that was very good and insightful and much related to what types of support are needed. A friend was involved in one of the articles and asked it was shared, especially by people in health and social care professions. I did. Well, within hours this other friend (the hot/cold one) completely went cold and has been for months. Any message is left with no possibility of back/forth chat. Literally a 180 turn - no commenting on my posts, no plans, nada.
I know she blocked everyone who posted differently about Brexit than she did. I didn't post about Brexit so wasn't one of them.
I miss the friendship and know she will come back eventually. It's really clear it is her issue, and that she can't cope with different perspectives, experiences etc and takes it very personally. It's like if you don't agree you think she's xyz. Which in fairness none of the articles shared said anything of the sort, all very much people's reflections. To me all this is a chance to learn, especially when presented as such. For her it's a bloody cheek that people think she's done something wrong - even though obviously the article wasn't about her, she wasn't tagged etc. Any difference of opinion = a slight against her. It must be hard to be her right now...
Hold your head high @DearyTearyMe. Hot/cold is a control thing and an inability to process/regulate emotions. Choose what type of friendship you want when it blows over. You be in the driving seat.