Why does my ex GF want to hang out with my best friend and his GF?

We were together for 3 years and broke up a year ago. She got a new BF right away and moved in together. After that I stopped talking to her all together. My best friend goes out with a friend of hers. My best friend and her were never friends. Now all of the sudden she's asking to hang out with them all the time (he personally does'nt like her, but she does'nt know that)..So why of they were'nt friends to begin with does she want to include him so badly??? He thinks it's the only way she can get to me beacuse I fell off the grid as far as she's concerned