I'm not sure I agree with just letting it grow out. A skilled stylist should be able to easily identify your natural color and add some similarly colored highlights throughout. These are my thoughts on how I would handle. My hair has always been very prone to breaking and damage, and I have gone through a lot of hair issues with overprocessing.
1) Olaplex steps 1 and 2. You can buy online. I would start with once weekly at home. Kind of pricey, but has allowed me to grow my hair an extra 4-5 inches using over a year, without damage from breaking, so I am a fan.
2) Deep condition/mask with every wash (which I would cut back on. Try to use dry shampoo and not wash very often).
- If you can get a heat cap and use this with a mask, even better.
3) Trim off anything hopelessly dead so hair looks healthier
4) Get a purple shampoo to help tone, but keep in mind a lot of these are very drying, making it even more important to use a good mask when you wash. I like Kerastase Masquintense, She Moisture mask, L'Oreal in the yellow tub, Neutrogena. Whatever you love that doesnt contain protein should be fine.
5) Find a good color who can help with the color. Lowlights can go bad (I have been there), but a good colorist should be able to get you to better place, even if it involves multiple colors of lowlights. Definitely use color safe shampoo after.
6) Try to avoid heat styling. Make sure you use a great heat protectant when you do. Look for ways to cut back. This could be a "compromise" styling. Like you still use an iron or rollers or whatever with heat, but you let air dry at night before styling.
7) Compromised hair can also need protein. Try every two weeks for a protein treatment at home. K-Pak is good and easy. Aphogee is probably the strongest, but a somewhat intense process and may dry out hair sensitive to protein. Always follow a protein treatment with a moisture only mask. (If you want to knock this out in one go...I like sitting around (working remotely) with the Olaplex. Rinse. K-pak. Jump in shower. Mask in shower. Done).
Good luck! You can bounce back with time, care, and patience.