Should I be worried about my dog's alarm barking?

Finding the barking annoying is really all the reason you need to work on stopping it. Even if she's not currently experiencing any anxiety or frustration, your best case scenario for doing nothing is that she continues to annoy you with her barks (and very likely influences your guests to bark as well). Worst case is that she eventually does develop anxiety and frustration (barrier frustration is very common for dogs who spend a good deal of time being able to see, but not interact with, something that interests them, even if they're otherwise very social and friendly) and her harmless alerts develop into a much bigger problem that will be far more difficult to address.

I'd suggest turning it into a game, like Look At That (LAT) training, so that the goal is to point out what interests her (dogs/people outside) and turn to you for a reward for finding the target. If you're consistent about rewarding her for looking quickly enough, she'll learn that she doesn't need to bark to let you know what she found, and after she's learned the game, you can phase out treats for praise.

I've only had one quiet dog my whole middle-aged life, and none of my dogs were ever aggressive. I think some dogs are just more vocal than others, and some dogs feel the need to "warn the pack" of any perceived dangers, whether it's children playing in their yard next door, or blowing leaves tumbling down the street. There are many dog training videos on YouTube that can help you with teaching your dog when it's OK to bark, and when it's not. I know, easier said than done, but I've been working on my dog using some of the methods and he is improving...just not quite "finished". Good luck!