My girlfriend is using a kinda dating app. And she said it's not for her. She just wants to help her friend. Is she doing something?

I found my girlfriend's pictures in a dating app. I just installed it to check her not using it anymore. But she is active. She said her friend's boyfriend is cheating on in it. Her friend asked her to help this. So That's why she started using it to check him cheating on in this app but she is using her own pictures.
But it's weird. And my girlfriend gave her account to her friend. So now her friend is using it. Guys do you think is it true? Or my girlfriend is cheating on me.
My girlfriend is using a kinda dating app. And she said it's not for her. She just wants to help her friend. Is she doing something?
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