Why my ex Girlfriend is showing her true colours?

3 year relationship down the toilet. About a month ago me and my lady decided to separate. That meant us breaking our tenancy agreement and living away from each other. There are a multiple reasons for our breakup the main one was trust and arguing. She was and still is one insecure person. We had a very emotional moment when our 3 years together came to end, so we hugged and kissed passionately one last time. During the one month post breakup, we kept in touch and she needed my help with buying, transporting and building storage furniture for her new room. We did all that in a weekend, it felt like old times making jokes, helping each other out and enjoying each other's company. Since then everything was cool and positive as if we were back to being good friends again - I mean that's how we started out! Until the last two weeks she's been acting very weird towards me like not answering my messages, not talking like before. She would blank me for ages until she wants to talk. So communicating with her has been difficult. At this point I thought maybe give her space which I did. While hanging out with a good friend of mine, she calls. I couldn't answer because my iphone was about to die and embarrassingly couldn't memorise her number to call back. She gets angry saying you never have time for while you're with your friends. I apologised the next day. Fast forward to now! She face timed me when she was abroad in Europe sharing her experience with me which was cool! Since she got back from her travels she's been acting very distant. I try to make contact but she replies I'll call tomorrow night, which never happened. So I called her yesterday to see how she's doing, she picks up and we talk. Then suddenly she became irritated and angry about a utility bill which is high but we must pay for. She was getting all worked up and then hung up on me. I called right back but no success, so I wrote a couple messages saying what's wrong don't be angry. She replied can't you see

Sounds like you have a complicated relationship.
you still seem to like her and she's still got feelings for you albeit some of them are angry ones
you've kind of just went off on a tangent in this message so its hard to know what you want to know about.
You're both still in touch, still seem to care… Maybe you should see if its worth saving.
your initial breakup didn't sound like the average one, hugging and kissing.
maybe you both need to live apart and date or even date other people to see if there's anything left.