Kidnapping is kidnapping. There is a discount for crimes committed while underage, but not enough to get away with something as serious as kidnapping.
Which is not what is happening here, because she isn't preventing the lolis from going home. There is no law against inviting random children to your home and feeding them junk food. Unless you knew one of them had allergy, in which case it's murder attempt.
Also, in many places there are "Romeo and Juliet laws", which make it legal for teenagers to have sex, as long as their ages aren't too far apart. But since Yuna is actually older than she looks (she is about 16, much older than the lolis), it would be illegal for her to have sex with them.
If I remember it right, they are actually speaking otherworldly language, but Yuna got translation magic when she arrived in the new world. So their food names are translations to our language.