First, I don't think you need to say anything about next year. If you didn't specifically issue an invite yet, just be sure that you don't say anything else that may lead her to believe that she'll be going with you. And if she does say something about it, then just say "Oh, I've actually agreed to take someone else this year. I'm sorry."
As for the trip itself, I've traveled with Debbie Downers and I get the frustration. She doesn't sound like she's a fun person to travel with even if she had payed for all the extras. I don't blame you for not wanting to travel with her again, even on her dime, for that very reason alone.
As for the paying for extras...I get why you're bothered by her lack of offer, but I don't necessarily think that she had any obligation to pay for anything for you. While I do think she should have bought you dinner or drinks, at least once, or offered something other than a verbal "thanks", I just don't think she's necessarily rude not to. You gave her a very generous gift for sure and she should have been outwardly grateful for it...however, I am firm beleiver that a gift must be given without expectation of compensation. And expecting her to pay for your extras is compensation.
Again, it would have been nice for her to offer to do so (you definitely shouldn't have been paying for her extras) and she does seem awfully ungrateful of this awesome gift, but if the financial arrangement was for you to each pay your own taxes and extras, then I really can't say she was etiquettely obligated to volunteer something different. She is obligated to send you a thank you letter I think and it would be a very friendly thing to do to take you out on her own dime sometime, but I don't think it can be expected.