Partner’s behaviour

Hello. Im in a relationship for 2 yrs. I need some advice and opinion on opposite gender friends.

To clarify , i think it’s ok to have opposite gender friends. I have male friends and my partner has female friends. I am just struggling at the closeness between him and 1 specific friend whom he always tells me is like a sister.

Here a some facts:

1. They text each other daily. Sometimes at a frequency of every few minutes. She updates him every little thing and vice versa. She rants at him about work etc.

2. They try to meet up 2-3 times a week. I asked my partner what do they do and why so frequent. He says it’s to hangout, do an activity ( meditate/ hike) or catch up over dinner. She would invite him to her house to meditate, just the 2 of them.

3. They have been on vacation together before and will share a room sometimes even a queen bed. He says it’s mainly for cost savings.

4. The first time he tried to introduce us, the conversation only went back and forth between the 2 of them. She never really asked curious questions about me.

5. She has my contact number but when he told her it was my birthday she just told him to wish me instead of texting me.

6. She knows my partner and I play badminton together alot. Recently, she invited him only to play with her and her friends . Her friend is the host mainly so i am also a little torn how i feel about it since she is not the host.

7. She invites him to join her many activities every week. She is someone who has many things going on daily.

   I try to brush off most of these but I’m reaching a point where i’m wondering if this is normal? If so, I guess i have alot of work to do on myself.