How do you let go?

No matter how old you are or what kind of person you are, it is guaranteed that many people have come and gone in your life. Some by choice, some by death, some you regret, some still on your mind. Well today I wonder how you let go.

Today is my ex-best friend's birthday! We met my freshman year in college and became inseperable. She introduced me to my current best friend, who happens to be her cousin. We did everything together and I felt like she knew me better than anyone. She got a boyfriend and didn't know how to handle still being a friend to me so I moved on. We made up a few months later and things fell back on track. We lived in the same house at that point and had some of the same classes. She started slacking in school and lying to her parents and expected me to lie to them too. At that point I was focused on school and had just met my current boyfriend and I couldn't go on pretending everything was okay. The final straw was the night we went to a party and got drunk and she left me to walk home alone for some random dude and one of her little cousins who she doesnt like. I was drunk and so was she and we had a huge blowout. We stopped talking and I moved out. She knew she could call me when she needed to and I the same but bff's wasn't what we were at the time. She moved on and found new bffs and I felt hurt and just angry b/c I saw what she was becoming. She was pining after a man who didn't want her, friends with girls she said she didn't like since I have known her, drinking all the time, lying aobut still being enrolled in college and her parents were oblivious to it. I called her one day just to talkk and we decided to meet up for dinner. We made up and started talking on the regular again, but not like before. She invited me to a house party with her new bffs and I went along with my bf and my bff (her cousin). We had a great time and things seemed to be going okay.

One day a few weeks later she got really sick and she needed money for a prescription, $150 to be exact. Although we weren't that close anymore I still had mad love for her and to help keep her healthy, I lent her the money because at the time I had it. She promised to give it back in 2 weeks and I took her word for it!

Well needless to say, she lied. I tried calling her after that and suddenly she had no phone. I found out 3 weeks later she got into a motorcycle accident (riding iwht some fool she didn't know) and suffered really bad burns to her leg. I called her friend to get in touch with her and basically let her know if something like this happened she should have called me, I would've been there for her. Anyway, after that she stayed MIA and I neer saw her or my money again. There is a lot of drama in between there but that is the end result.

Today is her birthday and there is a part of me that will always love her and one day I actually cried b/c I felt bad about how things turned out and my hubby told me not to b/c in the end she wasn't a real friend, but still it is hard.

So anyway, this all brings me to the question...
How do you let go of a loved one? Do you have to let go? Is it normal to always care?

*Happy Birthday Chica* if you happen to read this! I still have love for you but you can never undo what you have done.