Sarah Harmon, 22, from Presteigne, has spoken to politicians to offer recommendations to improve treatment.
She said a "one size fits all" approach of offering Cognitive Behavioural Therapy (CBT) did not suit everyone.
The Welsh government said it had worked with health boards to improve access to psychological therapies.
Ms Harmon said: "I'm fed up with hearing that CBT is the answer to everything. Borderline personality disorder doesn't respond to CBT but I've been offered it four times.
"You swing between extreme emotions and there doesn't seem to be a middle ground.
"It makes you quite sensitive to things and it can be hard to manage. When you feel something it's so intense, you just don't know what do with it."
Ms Harmon applied for one of the 20 spaces in her area for dialectical behaviour therapy, which was specifically developed to treat her disorder, but was unsuccessful.
"I felt like it was my only chance to get better and it was gone," she said.
But she kept applying and began receiving the therapy this year.
"I'm calling on ministers to make change happen. Above all, young people are the experts of our own experience, we know what works, so let us be part of the discussion, the re-design of services and future interventions," Ms Harmon added.
The Welsh government said it spends more on mental health services than any other part of the NHS, including on dialectical behaviour therapy.
Personality disorders are conditions that can cause a range of distressing symptoms and patterns of abnormal behaviour, including:
Source: NHS Choices
A woman from Powys who has borderline personality disorder has called on the Welsh government to tailor mental health services towards individuals.