İ do not know...the question is strange because self harming is haraam.
İt is like asking "is breaking fast with beer allowed?"
The obvious answer is NO! İt is not allowed.
The way I interpret this question is that the person in perticular already hurts (mutilates) herself and wants to know if she can continue her practices during fast.
She should know that hurting oneself is always haraam...so she should not do that at all.
It may not break her fast, but doing haraam things during the Holy Ramadan and fasting is extra bad.