Girlfriend's stained panties

Pics of my Girlfriend's panties from last few weeks, she says she hasn't fucked anyone else but this really looks like cum to me. Have posted in other threads but few replies. Her best friend is a gay black guy and she admitted she'd wanked him off before we started going out. She lives near him and often goes out with him and comes back with panties like this. I Love to imagine her getting filled with sperm. Do you think this is cum? I would love to hear ideas of what you think shes done, especially how you ended up with similar panties.. really appreciate replies x
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Dude......Cum doesn't stay in "that" form very long..(minutes maybe)....She would have had to have a Elmer's glue injection within one minute or two before that photo was shot..(provided it's not cunt powder mixed with ass cheese)....
"Nice asses only,please"