What should I do in this situation?

Okay I told u guys about this girl who has a boyfriend that was talking to me and I have a new problem with her now. I texted and asked her if she loved her boyfriend and she replied yes saying they plan to get married after college. I then told her sorry about the other nights she was with me and that I won't get in the way anymore while we are at school. She then responds with "no thanks you scare me". I have no clue what that is supposed to mean considering the night she claimed I scared her she was laughing the whole time and invited me to eat with her.

Another problem is she has 15 dollars of my money and I have a necklace of hers. When I texted her asking when she wants to meet up and give each others stuff back she responds it will happen on in the mean time stop contacting her and she will contact me. Like an hour after that she gets her friend to call my friend and told me to go pick it up. I'm starting to get irritated at this point so I'm just gonna keep her necklace and make her come get it whenever she decides to stop acting so immature.

Would love feedback on situation.

No feedback from anyone?

And something else happened last night. I gave her the necklace and she gave me the money she owed and I had to find her friend to get the rest they owed. While we were exchanging she was sounding irritated despite the fact that I have done absolutely nothing to her.

After I looked for her friend and couldn't find her I called and asked the girl if she knew where she was. While on the phone she starts to once again sound irritated and says that it is not her problem and to call her myself when I had already done so. I was getting irritated myself at this point so I closed the phone and sent her a text saying I did nothing to eithe one of them and that she needs to grow up and stop playing games. All of that with a few other colorful words and an exclamation point included. After that she actually called me and in a calm voice finally told me where her friend was.

Am I handling this right? And also sorry for all of the venting