I don’t want dues going towards his campaign
No dues have ever gone to any political campaign actually technically (staff time may get some liason assigned, but we can't give campaigns money). In fact we can't spend more than 40 percent of our budget on anything electoral or the feds shut us down for violating the 501 c 3 laws.
DSA (outside of the local chapter which was told not to do it but they have the independent right to) did not endorse her. She has no relationship to the org and pretty much everyone in leadership does not like any of the former Sanders campaign people (outside of the ones who have gone all in on DSA and labor) and does not talk to them. Nina specifically was never going to get national endorsement (nor did she even seek it) because of political disagreements and also everyone was confident she would lose badly.
I don't even know if she is still a DSA member.