Is my girlfriend messing around with this other woman based on pictures I see?

[M]

Ok so me and my best friend have kinda become more than friends...I think . Well we spent the night together and we fingered each other and kissed etc. It was my first time with a woman and she is always trying to kiss me and stuff . But she has this other friend she's had for YEARS and in pix together on facebook they are always tagged in , they hare holding hands or sitting on each others lap...and in the recent pic her friend is standing behind her and her arm is around her but her hand is placed right on my friends breast. Then people are commenting things like "are you two getting frisky?" and my friend commented back "you know it lol"
She told me she's never done 'anything' with her tho.