Hey Louisa,
Sounds like you're in a tough situation. I also happened to have met a rather troubled woman online. I don't think email and chatting can provide the attention some people require but it's worth a try. And internet counselling is getting more popular so I might add it to my resume!
As you may know, many cutters suffer from Borderline Personality Disorder. People with this disorder are often considerde difficult (to treat or simplu to interact with). This makes sense as characteristics of the disorder include instability in mood, relationships and self-image. a fear of abandonment and impulsive behavior. Borderline Prsonality Diorder can look similar to Bipolar Disorder and the term "borderline" originally described the border between neurotic and psychotic disorders. So, your support is important but I can understand if it can seem like too much.