Can girls orgasm randomly?

Ok so im in 8th grade and i was in class the other day just doing work and we sit in groups of three so the gir in front of me started moaning(silently where only people at the table could hear) and it looked like she was having an orgasm because it looked like she had her hands where her vagina was at(im not sure though cause i couldnt see because of the table) and she was moving from side to side like if she was pressing or feeling on something after a while of that going on she asked to go to the restroom and when she got back she wasnt doing that anymore. There was another girl at the table but we never said anything about it. So was she having an orgasm?