*SI trigger warning*

I'm in college seeing a therapist at school, and I'm going through a rough patch. I used to SI, but I haven't in 3 years, but I was having thoughts about it and I was thinking about telling my therapist. I don't know how she would react, mostly because we've never talked about it, and I really don't want her calling my mom (emergency contact) and telling her because she never knew about it. When do therapists usually use emergency contacts? Do you think that if I told my T about SI thoughts that she would use it?