I like pictures of other girls in bikinis on Instagram, my girlfriend snooped and found it
Could you explain your situation a bit more..
I am afraid since she found out that she will leave me now.
Your girlfriend is more likely to leave you if  you are liking other women's photos. You should stop checking out other women if you want to keep the one you have.
It's not that bad, I only check out Instagram from time to time.
Can you not see how she might feel jealous or insecure? This is completely your own doing. If you are unhappy with her you should break up.