How do I separate myself from Mom?

Seems like you are your Mom's "best friend" so she tells you everything, and I could see where that would become tiresome if you are the only person. How old is Mom, could she benefit from going to a Senior Day Care where she might develop new friends, thus find a new BBF [best friend forever] that she can talk with?

She is a frail 89 year old. Ues a walker and would never go to Senior day care or senior center. She doesnt live with me.

It's difficult to carry another person's burdens. And if we are constantly dwelling on another person's problems, complaints and ailments, it can become an obsession. If you can't stop thinking about her problems, I might consult with a counselor. Obsession is quite common. See what they advise. They may be able to provide you with some tools to help cope and to distract your mind from it. They may also be able to help you devise a strategy to set boundaries and establish your own interests.

I know it's so hard to try to enjoy life when there are issues with a loved one, but letting it ruin your own happiness is not productive. I think it's important to set aside the time you can devote to the talks and the contemplation and then set aside time for your enjoyment. A counselor could help you organize these times.
When things are so difficult for us to do alone, I say get professional help. It's amazing how much they can help.

I can't imagine having someone dump their trials and tribulations on you the moment you walk through the door. Sometimes it's hard to tell where one conversation ends and another begins. Especially when that person doesn't see you that often and doesn't have a social life.

Well, she's going to have to get one -- with or without the walker. She's not as helpless as you might think, so try to identify which upsets and/or problems she can handle on her own. Brainstorm a couple solutions. Since she doesn't want to do senior citizen centers, bring a few seniors you're well acquainted with. They just might entice her to get out of the house every once in a while.

Helping her build a social network will help you get back to life.