Here's a quick guide to help you see who Selena's tweeting and what she's tweeting about.

First, you can go to:
link]http://www.whocelebstweet.com/twitter/selenagomez/who/[/url][/url]

On this page you'll find a list of:
1) non-celebs she's tweeted (could be you?!)
2) celebs she's tweeted
3) celebs who've tweeted her

Note that you can click on This Month, Last 30 Days, etc to zoom in or out on her activity.

Second, you can go to:
link]http://www.whocelebstweet.com/twitter/selenagomez/talksabout/[/url][/url]

On that page you'll see a list of words that she uses a lot. Click on the word and you can see her tweets that include that word.

Third, you can see her tweeting back and forth with celebs. As an example, check out her chatter with Justin Bieber:
link]http://www.whocelebstweet.com/chatter/selenagomez/justinbieber/[/url][/url]

Enjoy and let me know if this was helpful!