Honestly, my answer is “no” it is not wrong.
I do not think it is wrong for any partner to leave another who is making things too difficult on a non-committed relationship (i.e. no marriage). There are many reasons why relationships fail, and sometimes relationships fail for NO good reason at all. Sz is a terrible, life-changing disease, and having been divorced in the past, I do not even think it is wrong for a marriage to break up if the person with sz makes a good marriage impossible. My marriage may break up over alcoholism, which is no where near as debilitating as sz.
If both partners are trying to remedy the wrongnesses in a relationship, it can endure. But only if both are trying.