I was under the assumption that the shuttle to AEON only ran from one of the Narita city stations. For a 4hr layover, you're not going to have much of any shopping time left if you have to do train+shuttle each way. Hence, I'd suggested Narita city as the only viable option for the OP. But I did not know there was a shuttle going straight from NRT terminal to AEON. Nevertheless, I see that it only runs 8x throughout the day. With that sort of infrequency, it's questionable as to whether it'd work out for the OP's transit timeframe.

I too do not recall a supermarket in the immediate vicinity of JR/Keisei Narita station. I just googled and there is a Yaoko ~10min walk from Keisei Narita Sta. That's the closest supermarket in that area, which to me is unreal. Anyways, while Narita city's konbini's and 100y shops may not carry all the condiments that a supermarket might have, the OP will probably still feel like she's in Jpn grocery heaven compared to what she's got in KC and they may be the only viable options time-wise should he/she decide to enter Jpn. Or she could do taxi to/from Aeon.