Is it ever too late to say thank you?

Context: I am a person who sometimes writes thank you notes. I think of myself as grateful for acts of kindness bestowed upon me. I'm careful to thank the person who picked up the tab for lunch or the one who opened a door for me. I often call the day after you've had me over for dinner just to tell you again how much I appreciate it. And then there are times when my manners go out the window.
I had a milestone birthday last year with a lovely party and lots of friends. It was the end of a long winter and Spring was still far away. A woman that is a new friend and the wife of one of my husband/boyfriend's friends gave me a very thoughtful gift. It’s a silver necklace with three small medallions on it with the engraved initials of each of my 3 kids. I have received countless compliments on it and every mother I know thinks it's an outstanding present. Add to that, the gift came in the mail, in an envelope, inside a beautiful card, with a wonderful note. It was so touching. Now, in my own defense, the card sat on the radiator at the front door for weeks before I knew that it was there. I opened it well after my birthday and told myself that I would call this thoughtful gift giver “tomorrow”. Well tomorrow turned into tomorrow and then a week passed and then several weeks passed and then the summer came and we started going to the cottage and then (as always happens), every time I thought about it I would cringe. The kind of cringing that you do when you feel bad about something but know that you are not going to take action because you are too much of a coward to truly know how to thank the person when you’ve been such a dolt by having not thanked them in the first place-the right way, right away. I have had the opportunity to make it right for almost a year and haven’t done it. I have even had the opportunity to make it right via my husband/boyfriend. He easily could have said to her on one of the 2 encounters he has had with her since the birthday. “Liza never takes off that beautiful necklace you bought her for her birthday.” The problem would have almost been solved. But I was even too much of a coward to tell him how hugely ungrateful I had been.
Cut to yesterday, I run into the thoughtful gift giver.i knew this moment would come and rehearsed it in my mind since. My friend Stephen came up with this great oversight strategy that involved telling her "again, I just want to tell you how much I love the necklace." Pretending of course that I thought I had thanked her in the first place.

She was as cheerful and friendly as ever. She has excellent maners. We were at the Love and Rummage Trunk Show at the Workroom and I was both delighted and sheepish to see her. And do you know what I did? NOTHING! I made chit chat and we promised to call so we could get together. What is wrong with me? After a few hours of self-loathing, I decided that I should tell my friends who were with me about my crime of omission. One of my friends told me that she wished I hadn’t told her because now she wasn’t going to be able to sleep until I was able to confirm that I had righted the wrong. So, here it is. Thank you Kimberly for one of the most beautiful, unique, precious and thoughtful gifts anyone has literally ever given to me. I love the necklace and today I wrote you a bonafide, old-fashioned thank you note. I'm going to buy a stamp and put it in the mail before I tell myself that I'll do it tomorrow.