that doesn't surprise me
It should, since there's no suggestion from the OP whatever that her given name is an Anglicisation of someone's Polish surname. Most young people called Whitney are named after a particular pop singer, recently deceased.
lazy tongues are pretty challenged by any word longer than two syllables
I don't doubt for a minute that you would know about the way Canadians and other North Americans speak, though I would challenge your point that they have trouble with words of over two syllables. As someone who has never heard Polish spoken in Poland, and with English as your first language you may well have difficulty with pronouncing Polish surnames, however here, in the old world people don't generally find it much of a challenge - I certainly never did
There are many people who have this as a surname
Rather few in fact (about number 900 on the UK ranking list, well below Kowalski and Nowak) and again no suggestion the OP is named after someone's surname. And of course the surname derives ultimately from a couple of rather nice villages which when you're old enough to travel as a tourist to Europe unaccompanied, you may enjoy visiting. Though if you go to Witney (the h vanished from one of them) avoid horseriding since you never know who you might meet.
And to the OP, Genowefa sounds lovely but is too archaic, Blanka is rare but probably your best choice as an equivalent.