I generally like frilly names, but Alexandria is a bit too much for my taste. I also like the sound of Alexandra better.
I love Alexandra and I would want to use it if I were not so fond of Alexander. It is common on the popularity charts, but I don't know any.
I dislike Alexandrea. It looks too trendy. I don't know any.
I think both names could rise again. It's a classic name and those come back over time.
I think both Alexandra and Alexandra don't need nicknames, nor does any name for that matter. People can always go by their full names if they wish.