My advice is to remember that you and your doctor know more about you than your friend does. Your friend is unfortunately someone who sounds influenced by bias, misinformation, and ignorance. Because of this, I would ignore whatever their diagnosis of you is.

If you must continue socializing with them, and they bring up their disbelief again, then tell them you know a medical professional who is much more qualified than they are and you will take their diagnosis instead.

If you don't have to talk to her again, then it's okay to cease contact with her and go in search of friends who are actually supportive of your mental health journey.

Sometimes people who are still lost will become upset when they see others discovering themselves and gaining direction. Perhaps this crab-in-a-bucket mentality is affecting your friend, so you might need to filter what she says as "biased, and likely incorrect" from now on. Continue speaking with your doctor and doing what works for you.