I completely agree. I am more interested in Charlie than he is in me. He took a little more of my time when he was little and required daily soaks, feedings, water changing, etc. Now that he lives outside, he helps himself to his own food. I make sure there is water and a heated house. We've gone on vacation and he was fine on his own.I spend almost zero time with my tortoise. Seriously...sometimes I go days without doing more than a simple glance into the heated house to make sure he's in there at night.
He has a heated house, fresh water, and a yard full of food and space to roam. That's good enough for him.
If you meet their needs, they will be fine. Attention and affection are NOT in their needs
If lack of time/attention is your issue, that doesn't affect a pet tortoise. A dog, yes. But the tortoise, no.
If you set them up properly, then you don't need to spend much time on their care.
I just want to share this so you can fully weigh your decision.
However, I would consider how long it will be before your situation changes. How many years of school do you have left? And then you'll be busy with a job and a social life. If the situation is temporary, then I'd say keep Shelly, but if it going to be years, I would probably give her up too.