What to do about the Gf of uncle saying concerning things about him to me

I (28,F) and my bf (28,M) havve been staying at my uncle’s (49) for a bit as we are doing internships where he lives.

He has a gf (44, F) who lives with him.

There are some things in their dynamic that concern me but I don’t say anything.

I am very close to my uncle and now to her.

They had a huge fight the other night, and my bf and uncle went on a walk so my uncle could vent, and I offered my support to the gf.

I was surprised by her really harsh temper, mean comments , cussing ect. and lack of appreciation she seems to have for my uncle.

When my uncle came back she was calm and nice.

I asked my bf if my uncle said harsh things about her and he said no.

It seems she has a lot of negative views/sides to her that she is not sharing with my uncle and I’m wondering if I should warn him or stay out of it.

Tl:dr: gf of uncle said concerning things about my uncle to me and I’m not sure how to navigate

I notice some things I don’t like in their dynamic but I don’t say anything