Depending on the facts of the situation, the opinion of a mature 16-year-old can be an important factor in a judge's decision as to where the 16-year-old lives. Unless emancipated, a 16-year-old is still legally not an adult with the right to self-determination.
If the 16-year-old wants to live with someone because that someone will let her drink, smoke, skip school, or otherwise misbehave, the judge likely will not be agreeing to the opinion of the 16-year-old.
If the 16-year-old does not want to go live with the noncustodial parent because she has not seen that parent in the last few years and would like to stay close to her present school and family members so that she can finish her high school, the judge likely will take a careful look at the 16-year-old's opinion.
The 16-year-old likely should seek some adults to advocate for her case. Such adults may include a trusted teacher, counselor at school, family members, friends, or anyone who knows the 16-year-old well enough.
Incidentally, someone should look after the financial well-being of the 16-year-old also. The 16-year-old may be a beneficiary of the deceased parent's estate. If the deceased parent earned enough work credits for social security, the 16-year-old may be entitled to social security benefits.
Someone likely should help the 16-year-old to review her facts and options with an attorney.
Can you choose? Yes. Does the court have to honor your choice? No. The other parent would have primary legal authority and that is not easily overridden. Some teenagers in similar situations jumo immediately to "emancipation" but many of them do not qualify.
If there is a court hearing on this issue the court will allow you to speak your mind and will take your wishes into consideration. However, you cannot force the court to just stamp your wishes as their determination.
Sign up to receive a 3-part series of useful information and advice about child custody law.