My ex will not return my stuff and has ignored me. Do I mail her stuff to a relative?

Here are some additional details:

She wanted "space" from me after 6 months. This happened a week before we were going to Thanksgiving to meet my parents. She said she had doubts about us and all that.

She called me 2 weeks later to formally break up because it wasn't "fair to me to keep waiting". She had a lot of anxiety over saying it. She promised to meet up before the holidays to exchange things over dinner, and as expected, she didn't call.

During all this, her best friend was giving me advice about what to do because the break up was a shock to her as much as it was for me. Her best friend also seemed interested in not telling me too much to avoid getting in the middle. I found out later, that her best friend actually asked a week prior to the break up how we were doing and was told our relationship was "awesome".

During the breakup, her best friend wouldn't get involved by telling me if it was someone else. 2 weeks after the formal call about breaking up, her best friend calls me up and asks me how I was doing (I was being very distant).

Her best friend goes on to tell me the ex wanted to see me before the holidays, that there wasn't another guy involved, and that she (the best friend) wanted to meet up with me in a month. Keep in mind, everything her best friend has told me would happen hasn't.

I've been very distant during this. I haven't pestered the ex or said peep to my ex. I did wish her best friend a happy new years and thanked her for her help. That didn't result in any kind of response (weird, huh?).

Here's the clincher, I have some of my ex's stuff and want to give it back. She has some of my stuff and won't give it back. I emailed her a direct and nice email the other day about exchanging things by meeting up, or mail. I haven't heard peep it's been a couple days.

I'm on speaking terms with her sister (she was really shocked too). So, I'm going to try to ship the stuff off to her sister. I don't know what's going on but, it feels like a very *weird* situation to say the least.

Don't get me wrong, I love her and it hurts, but I'm not fooling myself either. I'm trying to move on, I just want this stuff out of my place and my life to make that transition easier.

After having read this I understand that I still, honestly, haven't moved forward much, but, I'm on my way.

Any advice, tips, or insight would be appreciated!