I've said thank you a few times for the help they have given me in the past. I've also wrote them a note of gratitude and said just how much it has meant to me. When I gave her the note she thanked me and said it was kind.

I'm still not sure she truely knows how much I appreciate her support and stability, especially through hard times.

Maybe a letter/note? They can take it away in their own time and read if need be.