How to deal with a co-worker who continuously complains?

I work part time in a small office with 2 other ladies and have been in this admin role for almost 6 months. This job is to cover my bills while I build my weight loss coaching business on the side. One of the ladies complains all day about everything – our clients, contractors, other staff, her life etc. I do my best not to engage but listening to this complaining all day is really tough as I’m a happy, positive person who always tries to look on the bright side of life. I’ve been considering talking to the manager about her but he also complains a lot so I’m not sure about the best approach to take if I do this? Do you think this is a good idea or should I just focus on changing my thoughts to be more accepting of the situation?

This is the model I have been working on to try and change my feelings about the situation. Am I on the right track?

Unintentional thought model
C – Co-worker
T – I don’t like listening to her complain all day
F – Miserable
A – None
R – Nothing changes, she continues to complain and I continue to feel miserable.

Intentional thought model
C – Co-worker
T – This job isn’t forever
F – Hope
A – Talk to manager?
R – ?

Thank you so much for your help!