My fwb and what i'm doing saturday....?

so me and my fwb were really good friends before we decided we'd add the benefits part, its been a good two months so far, well she's been dating our mutual friend for a couple months now but they havn't made it official yet, and this saturday all three of us and another friend of ours are going to the mall together, now the friend she's dating doesn't know about our being fwb and i'm just curious why she decided to invite me and the guy she's dating occasionally to the same place to hang for a day. any thoughts? thx in advance for the answers. oh and for those who don't know fwb stands for friends with benefits. i'm 18 she's 20 and the one she's dating is 20.