Not having friends in bridal shower, help!

I think it would hurt her more to straight up tell her she's not a bridesmaid than by simply not asking her to be one. You could always give her a different role in your wedding, like a reading at the ceremony!

Just don't ask her, its her fault she's assuming and will be disappointed. If she brings it up why you didn't ask her and say you and your fiancé agreed to keep the parties small and you only have room for your sisters

Since you aren't even engaged yet, now is the perfect time to practice not taking everyone's advice about your wedding plans. You will likely receive plenty of opinions whether you ask for them or want them. And the longer your planning period, the more true this is. It's just how it goes.

But you and your future spouse have complete control over all the details (assuming you are paying for it yourselves), and so many things will be so much easier if you get in the habit now of keeping wedding planning discussions to a minimum with those who aren't decision makers. Be careful who you bring up your plans with and whose opinion you ask. If someone asks how planning is coming, just give a brief answer and change the subject. If someone offers an opinion that doesn't suit you, thank them and change the subject.

And finally, though this isn't just wedding related, you aren't responsible for preventing someone's feeling from getting hurt by your decisions that only affect you.

Your wedding isn't until 2023? I would wait to even think about asking until about 9 months before the wedding. If your friend keeps asking just say something like "thanks for your interest but we're not thinking about the bridal party yet", and change the subject.