Hey!
Don't worry at all about being an out-of-field student, there are plenty of girls who come from different schooling backgrounds (I've heard finance, teaching, business, linguistic, math, etc)! All you would do is take "leveling classes" (basically undergrad courses) and the program might take you a semester or two longer, depending on the number of hours you take a semester!
As for in-state vs out-of-state students....Most of the girls are from Texas schools, but I think it's mostly because UT-D is so well-known for it's COMD program. There are quite a few out-of-state students though, myself included! And most of the time, the out-of-state girls are granted in-state tuition as part of a scholarship given by the Callier Center
In terms of which semester to start, there's not really a ton of difference. There tend to be less people who start in the spring and most start in the fall. I started in the fall and graduate in about a week and a half. Although it's definitely possible to graduate a semester early! I have a friend who started a semester after me (in the spring) but was able to get enough clock hours and class credits to graduate with me in May!
Hope that helped!