will it be elfin lied or happy lesson or maria sama?

"Elfen Lied" is the best. The first episode doesn't really give you an idea of what the show is about. Once you've seen the second or third episode then you get a better idea of the show.

After that "Maria-sama ga Miteru" is also excellent, but it's a bit slower paced. If you and your cousin are female and/or aren't that into the slightly darker and occasionally violent bits in "Elfen Lied" then you might want to go with this instead.

Finally, and this is just my opinion, but I really didn't like "Happy Lesson". SLIGHT SPOILER AHEAD ----> It's a really weird premise, where a bunch of teachers like this one guy, despite the fact that he's kind of a prick, and try to turn him into a good guy. I really don't get it. Why put so much effort into helping a guy who doesn't really deserve it? The only episode I liked in the first series was episode 8. If you watch the three "Happy Lesson" series to the end, the "Happy Lesson: The Final" series ends on a really creepy note, IMHO.

P.S. "Vision of Escaflowne" is great, but if you ever get a chance to see the "Escaflowne" movie, don't. They rewrote the whole story in the worst way. I really loved the series, but the movie was awful.

Those are three VERY different anime. It really depends on what you looking for.

Elfen Lied is sad, and has lots of graphic action.

Happy Lesson is a harem anime with the twist that all the women are acting like the main characters mother.

Marimite (how it's usually shortened) is a refined school slice of life anime with yuri undertones.

Go with whichever one you want to watch. Although Elfen Lied is obviously the most popular and known of the three, and Happy Lesson is generally considered to be a mediocre anime at best (although I was at least amused and kept entertained by it).

Definately Elfen Lied. The first 7 minutes are probably the most bloody. The fact that it is violent and gory should not put you off. It works well to contrast the softer, sadder themes of the series. Elfen Lied has an awesome storyline, with a terrific ending.