Help sorting out how to approach a colleague please!

I am a family physician in an outpatient office setting. I work directly with a nurse 1:1 every day. We’ve worked together 5 years. She has a boss, it is not me (it is a nursing supervisor). We generally see our working relationship as co-workers, but I’m the final “authority” on making calls related to patient care.

She complains about patients and our work environment and work expectations every day. For example, after hanging up the phone she’ll comment “what’s wrong with people these days, their expectations are insane,” or “oh my god, not her again, she’s terrible.” When she sits in front of her computer after having been away from it drawing blood she’ll say “oh my god, i can never catch a break, 14 inbox messages,” or if there is a prior authorization she has to follow-up on for insurance (because they hadn’t gotten back to her yet) “oh my god, does no one do their jobs properly these days?” At the end of most days “I need to go home and have a drink after this insanity.” (she tells me she’s joking when she says this, doesn’t actually “drink her sorrows away”). I interact with her about 4-6x/hour (when I’m not in a patient room) and there is a comment like this in 80% of our interactions anyway.

My thoughts:
1) She is such a downer.
2) She’s bringing down the morale of the office.
3) All her complaining is slowing her down and making her less efficient.
4) She shouldn’t be talking like this in the office, other patients may hear her.
5) I’m not sure if I should say something

Prior to coaching I would feed off her energy. I’m much better at managing my own mind and energy, but I think I want to believe my thoughts 2, 3 and 4 above (despite her also being bright and a hard worker and she contributes to the office), though thinking such I feel frustrated (getting a lot of practice at allowing that feeling) and then I feel confused when I think thought #5. However, I’m not her boss, and that’s been my “excuse” for not having said anything to her about her complaining being inappropriate (nor has her boss said anything).

I generally ignore her comments, but if I have a few seconds in between patients I might say “hey, are you okay, what’s going on?” to which she’ll say “I’m here” or “I’ll get by” or I’ll say something positive like “we’re saving lives left and right, Bridget, strong work.”

So, I’m a little caught up in confusion. I would like help sorting through who I want to be here. I question myself: 1) whether her comments, which I’m calling complaining, are inappropriate in our office setting as I’m thinking they are or if I’m overly sensitive/just not liking them and judging them because working with her requires a lot more mind management on my part than when I work with the other nurses in our office and 2) if they are inappropriate (I want to think they are because if I owned my own practice and were the boss I would tell her she needs to keep her complaints out of the air space at work, offer coaching to help with such, and if she couldn’t do it I would let her go), I’m not sure how I should approach it given I’m not her boss.

After typing this I’m thinking I do want to keep my thoughts that her comments are inappropriate complaints, but I’m not sure who to be since I’m not her boss nor do I have a say in if I work with her or not. We are all employees of a larger healthcare system. I could talk to her boss about my concerns, but I’m afraid that will put a rift between her (my nurse) and I. I envision her thinking I’m “going behind her back.” Then there’s the elaborate plan of somehow secretly polling the office regarding their impression of how much complaining happens at work, how it impacts them, etc, and go from there. LOL . I sense I’m missing something obvious. Thanks for the feedback!