Keisei Line

Hello. I'm staying in Tokyo with my sister and in few days I'm leaving.

The closest station is Nippori and my intention is using the Keisei Main Line to get to Narita Terminal 1.
I was wondering if my sister comes with me without getting through the station doors in airport and returns leaving one station before or after Nippori, she would get charged the minimum amount on her IC card.

Will that work? I've read people doing full Yamanote circle and leaving +/-1 stop from origin and being charged the minimum.
Don't know if for Keisei works the same. If there's any system that detects you moved just one stop within 3 hours and then when leaving the door will beep, etc. I don't want she to have an embarrassing moment.

Thank you so much!

That probably would work, however it's technically fare dodging and isn't recommended.

A common principle regarding railroad fees is to pay as you travel.

I was wondering if my sister comes with me without getting through the station doors in airport and returns leaving one station before or after Nippori, she would get charged the minimum amount on her IC card.

It's a kind of cheating.

Don't know If there's any system that detects you moved just one stop within 3 hours and then when leaving the door will beep, etc. I don't want her to have an embarrassing moment.

Her IC card may be rejected at an automatic gate in the station near Nippori, then she may be asked about her actual route by a station attendant.
An IC-card fare-collection system (such as Suica or PASMO) is designed basically to choose a minimum-fare route when plural routes of different fares are logically assumable; however, in a questionable case it may hold a passenger up by rejecting his/her IC card at a gate.

I've read people doing full Yamanote circle and leaving +/-1 stop from origin and being charged the minimum.

It's a kind of cheating, too.

Inside the specified JR-East area in and around Tokyo, where a base-fare ticket is valid for one day, a passenger can travel by non-Shinkansen lines for a minimum fare only when he/she neither turns back nor comes to the same point nor passes through an exit gate.
When you travel in accordance with this exceptional rule, I recommend using a paper ticket rather than an IC card.

Tokyo -- Ueno -- Shinjuku -- Shinagawa (counterclockwise), inside gates on one day
: The fare for Tokyo -- Shimbashi -- Shinagawa (clockwise) is required.

Tokyo -- Shinagawa -- Shinjuku -- Ueno -- Tokyo -- Shinagawa (clockwise), inside gates on one day
: The fare for one circle and the fare for Tokyo -- Shinagawa (clockwise) are required.