Hi, help? - I'm going to paint the clearest picture I can - - excuse the length

So heres the thing. I've (F-28- Single) been working with this woman (F- 32- Single) for the last year, she's my equivalent role in another country. We've met 3 or 4 times, but we talk ALL THE TIME. Over the last 6 months its became more non work related - we talk on Whatsapp about books, plants, finding her new apartment - I helped her choose her furniture, cooking everything - its a real mix of serious and silly.

We disagree sometimes - work and non work related - she can be kind of a dick, and we can go for days without speaking mid conversation, and then its back to 100% normal again - and generally nothing is ever said about it.

The bizarre thing is, that despite all this - she is really uncomfortable and refuses to call me her friend. Its not that it bothers me, it's just something that I've never encountered before. - I should say that she calls everyone else we work with and heaps of other people her friends etc, but when it comes up about me its very much a 'friends? yeah no' situation. - yet we will then talk for hours about movies, music, hummus, dogs everything. I know a lot about her family, she always says 'everyone leaves' but yet he will call someone she's known for all of a month a friend / love and yet we've known each other for over a year and its like, saying friend is offensive or painful to her.

So is it just me - or a work separation thing? Anyone have any thoughts after a year its just a bit odd.