The US is a big country so I think you might have to narrow down her background to decide on a name. For example, where and when does your story happen, and where in the US does your character come from? What kind of family does she have? And what kind of story are you writing (is this a thriller, a mystery, for example?)?
Since your character’s 23, maybe looking at the top names the decade she was born would help. You can also look at surnames on this site, though I don’t know how accurate the stats are (you can just use it to look at surnames). And I think Spanish surnames are by and large intuitive, so you have little to worry about on that end, if you even do. (Though this might just be me.)
The first names that come to mind are:
Amber
Cassandra/Cassie/Cass
Jackie/Jacky
Jocelyn
Jessamine/Jessa
Vivian
Geneva
Danica/Danika
Danielle
Kennedy
Margo
Elise
Eliza/Elizabeth
Tess/Tessa
Yeah, I realised I should’ve been more specific in some areas. She was born and lives in a made-up American state, and the story is modern day. Thank you for the links, I’ll give them a try.
I really like the use of [name_f]Cassie[/name_f] (as a nickname for [name_u]Cassidy[/name_u], not [name_f]Cassandra[/name_f]) so thank you, I completely forgot about it. [name_f]Danica[/name_f] is also another great one, as is [name_f]Tessa[/name_f], [name_f]Elise[/name_f] and [name_f]Eliza[/name_f].
[name_f]Tamara[/name_f], [name_f]Lainey[/name_f] and [name_f]Noelle[/name_f] are just what I am looking for, as is [name_m]Hamilton[/name_m], [name_u]Hudson[/name_u] (great!) and Rivera. Thank you.