A bit of background...

My girlfriend and I are in a long distance relationship. She's in Asia I'm in UK.

She was with me and my fault over the Christmas period and we talked about going away in April to Taiwan.

She mentioned to her best friend (female) who asked if she could come with us. I'm not particularly close to this friend. I don't dislike her but I just don't know her.

My girlfriend was keen on the idea and gave me some reasons why it would be nice for her friend to come. These were she hardly ever gets to travel (a lie, she's always travelling) and she can't really afford to travel alone.

I don't really want her friend to come but this flagged up when me that maybe my girlfriend doesn't actually want to holiday with me. 

I think i would not be the asshole to say no to this. I'm wondering if this points to a bigger problem in our relationship. 
