Is she toxic?

What is this behavior? I have 4 younger siblings. The youngest is a nuisance! She always has to have the last word and try to get you to do what she wants or thinks.

For example, one of my cousins who we dont keep in contact with much reached out to me about her job search. I am well connected and have a large network of professionals. My little sister told me I should not speak to her because she is trouble.

Example 2, our family is invited to a memorial for my moms aunt who passed away last year. My mom was close to her. I told my mom I would take her. My little sister said we should not go because they didn;t bother to reach out or come to my brother in laws funeral this past November.

Example 3, my aunt wants to get some remodeling done on her home. I have been in construction compliance for about 20 years so I told her to be sure to check the contractors license for appropriate insurances, violations etc to be safe and also dont tell any contractor the budget. My little sister told our aunt the same thing the next day like it was her field of expertise.

Example 4, we had a brunch with 15 other family members on Saturday morning. Some family members were from over seas and others we had never met. My little sister kept talking about herself and saying random things to sway the attention in her direction.

Example 5, we recently stayed at a upscale hotel which is connected to a casino. I have been to this place probably a handful of times so I know the property, where to park so I can be closer to the hotel, restaurants etc. My little sister called me because she got there before me to tell me where to park, give me directions etc. I told her I know all of this as I have been there before.

is this low key narcissistic behavior? She is married with a daughter and I have picked up that her husband acts like her as well.