im sorry about the loss of your friendship impala. truly i am because i know how much that hurts. especially when you cant understand why.
all i can say though is that i have many many people that i got to care a lot about in my life and that i then stopped contacting because of my own issues. im fully aware its my loss totally and their gain whether they know it or not but i just couldnt and cant keep up with them. sometimes some of them contact me out of the blue after a few years and i contact them back once and thats all i can manage even though i still care and would love to find out how they re doing and become at least a little involved in their lives again.
i think if this person was someone you felt you could be friends with then she is probably not a bad or hurtful person but more likely someone who is hurting and confused and dealing badly and has thus hurt you in the process. that doesnt mean you need to make the effort to be there for her regardless of how shes treated you because if you practice good self care maybe backing off and acknowledging that it truly is her issue and nothing to do with you or who you are or even the relationship you two had might be the best option. otherwise you could also look at whether you think there is something about you or how you acted that might have caused her to stop the friendship and then work on that issue for yourself so you develop positively as a person. whatever way you choose to go though, my belief is that you will only be able to deal with this if you make it about you and not about her. because you cant change her and what we cant change we must accept. once you are happy with who you are and how you acted and are therefore secure in yourself as a good and worthy person then it can become about helping her if you like but until then... self care.
again i do empathise with your pain and these are just my thoughts. quite possibly im way off in them but just in case you wanted my two cents i thought id post!
best of luck in dealing with this impala
take care
biiv