The adjacent congressional district (CD-15) flipped from blue to red and the Democrat received support from Justice Democrats after she won the nomination. FWIW, Bernie and Cisneros were at a rally in McAllen for Michelle Vallejo in the week prior to the election in CD-15 and their support wasn't enough to get Michelle Vallejo elected.
If Cisneros won the nomination in CD-28, I suspect that some of Cuellar's supporters would have not voted for her in the general election. Ultimately, it was Cuellar's support from the business community and his tenure in Congress that clinched the victory for him. Cisneros did not have that support and her occupation as an immigrant rights attorney is not popular in South Texas. At this point, Cisneros has lost three elections (2020 primary, 2022 primary, and 2022 runoff) -- she should take those results as indicators to concentrate on her job as an attorney and end a campaign that ran over two years (and still continues if you read her bitter concession to Cuellar).
Meanwhile, I'm disheartened that the congressional district where I was raised (CD-15) flipped to the Republicans. The results of the election did not surprise me though since that district was the most vulnerable of the three South Texas districts and I've mentioned that belief several times since February. I'll take solace that all three South Texas congressional districts didn't flip to the Republicans despite what other Democrats may feel about Cuellar. A win is a win--no need for second guessing or "what ifs" until the next primary.