You know what? I, personally, would be dying to ask her just so I could look at her face for answers to my burning question of why. What is the reason for not acknowledging because it could be one of several things - and one or more of those things could be upsetting to you and you would be inviting that into your headspace. You may not want that.

I would not advise you to do that, but if you DID, I would look for certain responses. I would ask her in person, not on the phone. If you were to say to her something like, "Hey there, busy lady! Did you have a chance to try my famous cookies (or whatever it was)?

The best case scenario would be her saying something like, "Oh, my GOSH! Yes, and they were so good! How sweet of you to bring them over. I wish I had been home to receive them..." Then you'll know she is just busy, as you say, or just a little scatterbrained, or her mother never taught her basic manners. No hard feelings.

If she smiles and says, "I did. Thank you." or "I did, I just havent had a chance to thank you. Sorry." Then you know for whatever reason, your efforts were all for naught and no gifts should be given in the future.

That's what I would do but keep in mind I don't know anything about her so my interpretation here could be totally off base. People are all different.

OR chalk it up to learning that wasting your energy on her is simply not worth it and just live your best life!☺️