Hello, Your second sentence is not quite right. I would write “Although she wasn’t looking, I waved to Helen”. Or “Helen wasn’t looking, but I waved to her anyways”. You really need a conjunction or an adverb to give coherence to the sentence. Your third sentence should be written like this: When i waved to Helen, she wasn’t looking. Finally, yes they all mean the same!

1 and 2 have the same meaning but the referencing in 2 is weak because you have put the pronoun before the noun. 3 has the same problem as 2 but is otherwise correct. Better: "Helen wasn't looking when I waved to her." 4 looks odd because of the use of "while" with an activity that didn't happen at the same time as a short activity (waving). When is better: "When I waved to Helen, she wasn't looking." 1 is most natural.