I think Russian transliterations tend to vary with the language. For instance,
Yuriy is spelt Youri in French. Lenin is Lenine in Portuguese. Both spellings are valid.
I stick to my point.
Walentyna would be anglicised as
Valentina. Valentyna looks as though it would be pronounced as [val-en-TIE-na] in English. The 'y' adds nothing to the name but further confusion towards the spelling.
I'd rather use the original spelling (frankly, if people can learn how to pronounce
Nevaeh, would
Walentyna be that difficult?) or chose a name that works in both languages.
An example. Imagine I love the name
Audrey and want to use it for a child. I live in Portugal, where the name would most likely tend to be pronounced as [OW-dray]. To prevent this, I decide to spell phonetically as Odri - but because it doesn't feel English enough I settle on Odry. And then I say to people my daughter has an English name.
This is an exageration, of course, but I'm trying to point out that what you're doing is a disrespect towards the original language. If you want to use a Polish name, chose a Polish name. Follow the rules of Polish ortography - in Poland variant spellings aren't allowed, unlike what happens in the States, where you can have
Emily /
Emilie /
Emilee / Emmaleigh. Valentyna can't be considered Polish at all.
I'm sorry if I'm being a pain.
Lew /
Lev is one of my favourites, btw! :D