Aright, Seddit, here's what happened:

So I said, "this weekend I'm baking and since you're the expert, you should help". Preceding was text banter and talk about this and that. I thought I had developed interest...

But then she said, "this weekend is not good, my sister is coming down for the weekend and my dad and I have plans". I said, "how about Monday night" and she said, "I'll let you know".

What does "I'll let you know" mean? Do I text her on Monday or do I just let her get in touch with me?

tl;dr: What does "I'll let you know" mean? Do I text her on Monday or do I just let her get in touch with me?