That doesn't mean you owe it her to stay. No good leader would be happy about their workers finding a much better paying job.I've been with my TL since I started in Target and that was 5 years ago so yes, we've been through a lot and I do owe her part of where I am now. I learned a lot from her.
You should learn new skills and used them to get ahead, not learn them and make the same when you can make more. I took a side job learning electric work for a company, they honestly taught me a lot and wanted me to grow with the company but they paid me like shit. I have another offer that paid better and I only needed the experience I got from the first job so even though they trained me well and wanted me to stay, I have to leave for the better paying job
Gotta do what you gotta do to get ahead. Even if your TL likes you, they probably won't take a cut in hours to keep you at 40 if your payroll goes to shit