When we say that Ada Lovelace was arguably the world’s first computer programmer, that “arguably” isn’t thrown in there because of questions of definitions or precedence – she definitely wrote programs for a computer, and she was definitely the first.
Rather, the reason her status as the world’s first computer programmer is arguable is because during her lifetime, computers did not exist.
Yes, really: her code was intended for Charles Babbage’s difference engine, but Babbage was never able to build a working model – the material science of their time simply wasn’t up to the challenge. Lovelace’s work was thus based on a description of how the difference engine would operate.
Like, imagine being so far ahead of your time that you’re able to identify and solve fundamental problems of computer programming based on a description of the purely hypothetical device that would run the code you’re writing.
(Having no actual, physical computers on which to ply her skills, she then turned her attention to developing mathematical formulas for beating gambling establishments at their own game, which demonstrates that she anticipated not only the practice of computer science, but also the culture.)