I've gotten myself into a weird situation.

I have known this friend for a little over 10 years. Recent events have brought some issues to light, mainly that this friend feels much closer to me than I do to them. They have expressed feelings to me and said things that make me question their rationality. One example is that this friend told me that they feel that their life would be over if I were not their friend or if something happened to me.

I am a 30 something woman, as is this friend, and this behaviour and intensity of emotion that she is expressing to me make me very uncomfortable. I enjoy spending time with her but I do not want to be responsible for her happiness or, in essence, her life. She is always telling me she is worried about me and I find this to be very disrespectful and annoying. I'm an adult and I can take care of myself, I do not need, nor want, someone to worry about me.

I feel trapped because I did not realize the extent of her attachment to me and if I had I would have attempted to end the friendship much much sooner, but now that it has gone on for so long I feel as if it would be a horrible thing to do to her.

Any advice is much appreciated.

Speak frankly, but gently to this person and explain that although you value her friendship, you don't feel the same way about her as she feels about you. If she loved herself as much as she claims to love you, then she wouldn't be so needy or demanding. Love and respect yourself first and others will follow. Nobody wants to feel trapped or responsible for someone else's happiness. We all are responsible for our own happiness and cannot make anyone feel a certain way. We choose to feel however we feel. She's making some bad choices and blaming you for them.

Find a polite way to tell her that you are very capable of taking care of yourself that you do not need anybody wasting energy on worrying about you.
She sounds like she either has insecurity issues and/or is very co-dependent.

I wouldn't say cut all ties with her but maybe encourage her to spread her wings and find her own interests.