Even if you were over 18, you should be able to attend together since you're family and you're traveling together.
This is particularly true if your baggage is at all intermingled, i.e. if you have things belonging to each of you in the same bag.
I'd present together.
You'll certainly be advised if this isn't acceptable, and I fully expect it will be acceptable.
travel.stackexchange.com/users/62876/Jim MacKenzie
Your age doesn't matter.
Go together.
I usually do so.
This simplifies the control of the immigration officer, especially if your mother doesn't speak English or if she expect that you will guide her to the city and country.
In any case, to reassure you, you will do some queuing, so check how other people behave.
If a new policy is being followed, you will find that other people will be split (from their group).
travel.stackexchange.com/users/53544/Giacomo Catenazzi
Short Answer: If you're traveling together, you will go together, regardless of your age.
I've repeatedly flown into the US from overseas, most recently last month.
My family is mixed US passport and Green Card, and we don't have the same last name.
Regardless, we've always been processed with the automated machines.
If there's someone with a US passport in the group, and everyone else has the required visa, then you all go straight through the automated system.
You can choose your preferred language for the process at the kiosk.
A non-US citizen will have to submit to a finger print scan at the machine, everyone must answer questions about their trip, and everyone will be photographed.
At the end, each person has a printed "receipt" to carry, and eventually give to a customs agent.
You interact with a human afterwards, but almost everything is done by machine.
There's a long queue beforehand, so use the restroom or fill your water bottle immediately after you leave the plane.
We've stood in line up to 40 minutes.
travel.stackexchange.com/users/73267/Ashley H
Newark is listed as having the Automated Passport Control machines.
If you are eligible to use these then...
The kiosks allow people residing at the same address to be processed together.
I believe for visitors that means those who will be residing at the same address (including the same hotel)
while in the US, not a matter of living together in your country of residence.
Certainly you and your mother should move to a machine together and start entering your details - it will guide you if you need to do anything different
travel.stackexchange.com/users/36472/Dragonel
I know the question was about US, but I guess it also depends on the officer's mood.
I was travelling to Finland last December on our way to Finland
the officer asked us to go border control station together, while on our way back another officer specifically told me to keep the distance between me and the control station while he was looking at my gf's documents.
travel.stackexchange.com/users/73293/aga
As others pointed out, age shouldn't matter.
If I travel to the USA with my spouse, usually we approach the officer together -- it has never been a problem.
Except the last time.
We then flew into JFK, and at that moment, I was a "returning ESTA visitor", and my spouse was not.
Which meant, we got sorted into two different lanes.
But if that doesn't happen to you, and you're both queuing in the same lane, just approach the officer together.
The worst what will happen is the officer saying one of you have to wait till the other is done.
travel.stackexchange.com/users/None/
My mom and I are traveling to New York City together soon and I will be 17 years old by the time of travel. The airport of arrival is Newark Liberty Airport(EWR).  Will we have to go one after the other to the border control officer or can we be together since I am still under 18?
My mom and I are traveling to NYC together. Can we be together at the border control station or will we have to go one after another?
travel.stackexchange.com
<usa><air-travel><customs-and-immigration>
travel.stackexchange.com/questions/109071
travel.stackexchange.com/users/68050/Itay080
Unles specifically instructed otherwise, you can go to the machine or desk together if you are residing at the same address. In most cases you can enter through the machines and approach the customs guard together though there are some rare exceptions to this i.e. when you are required to stand in a different line from your mother, when an officer tells you to separate or when a customes officer tells you to wait while he checks your partners details.
Regardless of your age you should be able to use the machines and approach the customes officer together. There are some instances where you may be placed in separate ques. In some cases you will have to deal with the officers demands and separate if they decide to separate you