This discussion won't get anywhere, flandre IS NOT rumia, end of story.
They have completely different spellcards, themes, backgrounds, appearance, personalities, etc... this theory about flandre being rumia is really nonsensical, I must say. Zun never even gave a word about this, unless he proves otherwise I'll never believe such thing. Some features alike between them are mere coincidence.
It's as stupid as saying "Suika and Yuugi both are onis who like to drink, do parties and fight the others" So, does that mean Suika is Yuugi as well?