We went through the same situation Aug,2024. Augustus (Gus) our Basset Hound was 11 years old. It was one of the most difficult decisions we ever had to make. The sadness is difficult and definitely comes in waves. Just remember the good times you had with her and she had with you. They're only here for a short time. Which reminds me of a poem.... "People are born so that they can learn how to live a good life — like loving everybody all the time and being nice, right? Well, dogs already know how to do that, so they don't have to stay for as long as we do"
It gets easier but sometimes for no reason out of the blue you'll think of her. Just smile and be glad she was in your life. Hell, I just teared up last week thinking about Gus.
Not sure if you've ever read the Rainbow Bridge Poem..
https://vet.uga.edu/wp-content/uploads/2024/12/The-Rainbow-Bridge-Poem-Hand-Out.pdf