Worried parent

My daughter has had autistic traits most of her life, she was never formally diagnosed as she did not want to be ´labeled’ at school so between us we had coping strategies for her meltdowns which worked. She is now in her mid 20’s is in an extremely stressful job & is with a toxic boyfriend which she defends constantly, she has low self esteem & her meltdowns seem to be happening more frequently. Wgen I have mentioned getting a formal diagnosis she shuts me down, saying  she doesn't feel like a formal diagnosis will help as she has coped this long so will carry on the way she is. But I feel things are getting worse & am worried she is heading for burn out. Has anyone got any advise that getting a diagnosis will help.