I have two close friend who know that i SI.. they are from music camp that i go to.. well i feel that i dump too much on them and i suck them dry emotionally.. i tend to lie to them too... I dont tell them i lie. I only told them once and i got the same reaction u did. I dont know if thats the correct answer.. but i can relate... I think u should tell her ur sorry and why u lied.. It might also help to give her information about SI.. I did that with my two friends and it works.. they know that if i dont want to talk they dont pressure me.. they just say think before u do anything rash.. And usually i tell them the next day if i did anything... What would help is make out a contract... this is the contract i made with my friends:

1. I will not cut only if its a last resort (after all other interventions fail)
2. If i do cut i will take care of it.
3. I will try not to be a perfectionist
4. I will talk to them if i have a problem
5. I will keep them posted on how i am

This is a copy of mine.. u can make one of ur own for u and ur friend.. and also let ur friend know what u expect from her and dont want to expect from her...

Hope this helps..