There are no silly questions, just lots of silly people 😉 Me included.
This title has a lot to do with region. For most of us, we would use Miss just for little girls or very elderly women who never married. For some, it is used for most unmarried women.
But, Ms. can be used for all unmarried or married women of age to marry–usually over the age of 20. So, it is your choice.
Actually, I use Ms. even though I am married. I love my husband and have a great marriage, but don’t want to be defined by my marital status.
Ms. is usually a safe title if you don’t know a woman’s marital status. Use Miss for those whom you know are unmarried and are formal in nature or from the south. This is also used for young girls.
photos via SMP