Is it okay to include this menstruation scene in a children/young adult's book?

Three girl characters were on the middle of something (annoying the main boy character, actually) when all of a sudden the leader of the three had a strong menstrual gush (that part of her white jeans instantly got stained red, and there were drip-drips..)
Update: And the main boy character embarassly looked away, his lips very tight, fighting hard not to laugh.
Update 2: "But i'm not a teenager yet!" the leader of the three complained, but at the same time, looked very fascinated.
Update 3: @Mutechords Gawd! But that's brutal! hahaha :P
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