The SCOTUS argument was that Texas did not have the right to act for PA, if I understoood the issue. Seven voted NOT to hear the case. Alito and Thomas wanted to hear the case but also agreed that Texas had no rights regarding the PA situation, so basically 9 to 0 against Texas. Isn’t protection of one state from the suits of another part of what Federalism is all about???
Not necessarily, the purpose of the Supreme Court under Article III is explicitly "to resolve controversies between the States".
They very well may not have found in favor of Texas and the other States, but by definition we have standing to be heard.