Would people ume one is bi/ if they have a pic of a woman in a bikini as her cel wallpaper?

See my friend's bi and she's afraid people will find out she's bi due to her wallpaper. The wallpaper is a black and white pic of her favorite celebrity in a bikini. So would people ume she's bi? Would a straight girl do this? If so what excuse could my friend use so people will not find out about her being bi?