I was given this name too in 1957. My cousin went to school with the actor Sal Mineo's sister, Serina, and there was another girl in the town of Mamaroneck, NY where Sal's family and my family lived. Named Serina Sexauer. So, my mother thought it would be a good name for her new baby. It was a difficult name to have as a child, but I love it now.
Serienna is pronounced 'SEH-REE-EH-NAH', not 'SEH-REE-NAH.' Anyways, I really like this name. Both spellings, Serina and Serena are good. This was the name of one of the InuYasha characters, Serina, a long with her sister Suzuna. I also like the name Sarina (SAH-REE-NAH), but it's a different name than this one.
I personally love this name and I think that it is better written this way than S-E-R-E-N-A. And most people don't pronounce it right because it is pronounced like the other one but just written differently. I believe that this form of Serina is more French.
I was given the name in 1962. When my mother needed a girl's name, all they had were boy's names. My mother had read the name in a movie mag - it was the star's sister's name. The star was Sal Mineo the young boy in Rebel Without A Cause. It is a name I have had to grow into. Also I find a lot of people don't know how to pronounce it. Or spell it. And good luck finding it on any of those little bike tags they used to put out. But I love my name and would never change it.