I'm sorry to hear of your loss. This sounds like a tough time for you!
Go with your instincts. It sounds like you feel that a spell of home education could be good for your daughter.
If online school is stressful for your daughter but you think she needs routine, the two of you can work together to create a routine which doesn't have to be based on very stressful situations.
For example, your routine might include getting up and having breakfast at a certain time followed by a walk to the shops and doing housework together, then reading a book of her choice for an hour, and getting some exercise which could be a choice between swimming, trampolining or dancing to the radio. Then listen to a podcast, do art or music, and so on.
You could think in very broad terms where your daughter's social needs are concerned. She might enjoy the company of other teens, but there are other ways for her to feel connected and happy also. Could she do some voluntary work, perhaps with you if she needs the extra support right now? The two of you might work together in a charity shop, for example, or join a "green gym" to do conservation work in a team, or deliver library books to elderly people who can't get out easily. You might join a drop-in community choir together. Those types of activities would add structure to your week. Animals and younger children may help your daughter to feel needed and admired without putting great social demands on her. Does the local animal sanctuary need voluntary dog walkers, or would you want to join the Cinnamon Trust? Do you have young friends or relatives who would like your daughter to visit and play with them?
You may have a long and difficult road ahead. You've tried several avenues already to help your daughter. Don't be afraid to keep experimenting to see whether you can find the right way forward.