I have had my name spelled in two ways in katakana - and I don't think it is possible to say one is right and the other one is wrong. My then boyfriend bought a keikogi for me in Japan, told the staff in the store my name, and they wrote it down - ha-n-na. In the other case, a visiting Japanese teacher brought the order with him home; he chose to spell my name ha-na rather than ha-n-na. Personally I think ha-na might be a slightly better spelling, but both should be OK I guess.
Maybe he thought that hana like flower (花) might be nicer. It is also pronounced in Japanese as two equal length syllables. Is that close to the Swedish pronunciation of your name? Or would han-na have been better?