Struggling with my challenging 18-year-old daughter

I have an 18-year-old daughter who has always been a handful, even from a young age. She’s had intense temper tantrums throughout her life, and they still happen now. She can be manipulative and struggles to maintain friendships. At home, we have to constantly walk on eggshells—choosing our words carefully to avoid triggering an outburst.

Since she started high school, we’ve suspected she might have high-functioning autism. We haven’t directly told her this but have encouraged her to seek help. She refuses, and we’ve respected that.

However, her behavior is becoming increasingly hard to deal with. It’s exhausting, and I’ve reached a point where I feel like I’ve run out of patience. As much as I love her, I can’t deny that my tolerance for her behavior is wearing thin.

Has anyone else been through something similar? I’d appreciate any advice or tips on how to cope and support her without completely burning out.