Hi! Well, my mom is a stay at home mom AND she works from home. So I can see where you're coming from. There are so many simple, small ways you can help your mom, and it's so sweet of you to think of her, that's very thoughtful =) Well done hun =]
Firstly, you can let her know you will clean your room. Take 5 minutes before you go to bed to just tidy some stuff and that way you take that off your mom's back. And on the weekend, you can clean your room. (mop/sweep whatever).
You can make your own school snack or a small meal of the day. Organise your time, and set apart just some time (like 1/2 hour) to do something in the kitchen for your mom, whether it's putting the shopping away or setting the table, washing the dishes etc. I can assure you that's a great relief - like someone offering to write an school assignment for you - Woo hoo yeah? :)
Wake up a teeny bit earlier to make your bed. Technically, it takes 2 min. to make your bed - can you give up that much for your mom?
And then of course the simple things, that perhaps annoy her, like you fighting with a sibling, leaving the TV on when you're not there, or I dunno what the rules are at your home, just try to reduce them. It will make your mom feel better, and less tired. Try to listen to her, and don't give her a hard time. Narrow your 'wants' to your 'needs' (as much as possible, of course). And take it easy, you're only a child. And if you see her taking a break, and she feels like talking to you, spare some minutes to have a chat with your mom. You'll enjoy it and so will she.
I'm gonna take my advice and put it into practice, and get off the computer =) Thanks for your question, it made me think, and once again, how sweet of you to think of your mom, I'm sure she'll appreciate every single thing! Take care :) Good luck, hope I helped xxx