There is certainly nothing abnormal about this. It is very hard for young children to get prepositions (on, off, under, behind, above, etc.) straight. And, if you think about it, you can understand why. Take “in” and “out,” for instance. The one to use depends on your context or your frame of reference. Let’s say your daughter is in one room and wants to be in another one. She doesn’t think, “To get in the other room, I first have to get out of here. Her mind is focused on getting into the other room. So she might say, “Let me in,” meaning “Let me in the other room.” If you were in that first room and wanted to go somewhere else, you would probably simply say, “Let me out.” I hope that is clear; it is difficult to make the point in a few words.
Playing little games with her with some of her favorite toys will help her develop an understanding of these concepts. Ask her to do certain things with the toys, all of which involve these tricky prepositions. “Put the doll under the table.” “Put this raisin in the bottle.” “Get the raisin out of the bottle.” You can think of many variations. She will love this game—and so will you!
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.