So, there was some accusations of sexism recently in regards to how Sinema is treated compared to how Manchin is treated. I feel I've explained why I make a distinction between the two numerous times, but 538 just put out an article featuring some interesting stats that make my argument pretty clear.
https://fivethirtyeight.com/features/kyrsten-sinema-is-confounding-her-own-party-but-why/
It's the first table in the article. It looks at how Democratic Senators voted during Trump's presidency and compares how often the Senator voted with Trump to the expected percentage based on partisanship of the state they are from. Manchin voted with Trump 50.4% of the time, but based on how red WV is that is a difference of 38.9% more blue compared to what would be expected. While he is frustratingly moderate, he is frustratingly moderate in a seat that should never be blue and him holding that position is significantly better than every reasonable alternative.
Sinema funnily enough, also voted with Trump 50.4% of the time. However, this is actually 10.6 percentage points more red than would be expected based on the partisanship of the state (a number that wouldn't be surprising coming from a Republican).
Now, you might be thinking "But she's in a purple state so she also has to play the moderate sometimes", but that 10.6 percentage points is the single greatest difference of any Democratic senator. Other moderates lean blue about 20 percentage points more than would be expected, but not her. That is what makes her actions so positively baffling and make it pretty clear that there are better alternatives for her seat.
What makes her even more baffling is the fact that she used to be a Progressive. When she was in the House, she was one of the most ideologically liberal members, but as soon as she got to the Senate, she flipped to being one of the most conservative members. This is also what makes her donors particularly interesting as a possible explanation for this significant flip. There could very well be other motivations, but her actions are incredibly strange and she deserves to be ditched by whatever progressive base she has remaining at this point.