[Facts] Re: meaning of the names
Most unique names are invented by combining name elements or names. So for the true meaning, you'd really have to ask your parents; otherwise you can just guess which elements they combined. My guess for your name would be Tasha (from Natasha) plus Sheena.
However, the name may not be unique or invented by your parents. It may be a Native American name (Cheyenne).
I googled it and found several instances of it used as though it were a Native name (Cheyenne). I also found Tashina on a page where a person had listed many names and said that they'd been unable to find any info on them. I'd suggest you contact Native American heritage interest groups to seek info, if nobody here speaks up with any.
- chazda