I know this thread is old, and you may have another Goo by now, or may have rehomed Tepal. But I just wanted to share my experience in this area with you!
I'm in the same situation. One of my girls died in October, so since then, I've only had my one little Goo. I was super worried about her dying of loneliness, or some such thing - you always hear that you should never keep single Goos. (I still hate ever having to leave her with a sitter, I try to take her with me whenever I have to go somewhere.)
But we're doing really, really good. I schedule at least 30 minutes to spend with her out of her cage everyday. We've gotten soooo much closer. Now we groom each other (oh, that's the BEST feeling!! Having my face or arm groomed, it's wonderful!), we talk, and she has taken to sitting on my shoulder.
Just keep doing what you're doing, and don't give up. Tepal knows you well, and loves you, and that love will only grow and deepen as you have to depend on each other.
I sure hope you're feeling better now, I know what a struggle it is, I fought with it too. Finally, my heart is ready to start thinking about bringing home another Degu, but I'm not in any kind of rush. I sure hope things are going well for you. I can tell you love your Tepal very much, and I know she can feel that too!