Nisse if you're talking aboout small forms of these names then surely there are lots of variations.
Irina - Ira, Irisha, Irochka, Irinka.
Olga - Olya, Olenka, Olechka.
And so and so and so...
We prefer to use small forms instead of full names:)
Hey even my nickname is a small version:)
But you have to admit that there are many many girls with the name Natalia -or a varient of it. I have a daughter Natalie (but it is a very uncommon name here in U.S.). I tried not to write to girls with the name Natalia because of my daughters name - although I wroy=te to a few Natashas (but not Tim's !)
Now Ludmila's, I wrote to a lot of them! Lucy is of course Ludmila. Maybe their names somehow shape or go along with their personalities .