How do i manage this? 5.5e

I have been in a campaign for nearly 3 years with my partner, her friend and her friends partner dming.

The story has been fantastic with a couple parts being rather heavy focus on the dms partner but recently it's starting to take over. The other players have received very little progression while their partner has levelled up more, gets individual sessions that we have to sit through and has also now received their 3rd character that they can chop and change between as they want and the story will be made to fit.

I have tried to bring this up and I don't seem to even receive responses about it. Kinda just gaslit.

I don't want to give up as the story has been fantastic but the favouritism is grating.

I am at the point where I'm debating on going full chaos with my character out of protest.

Why do y'all think I should do?