Unlike most foreign ships (and some Japanese ones, even) Gotland's in-game lines have her drastically transition from a semi-formal introduction line into acting completely chummy with the Admiral and the rest of the naval base (being willing to accept or receive displays of physical affection, playing pranks on the other shipgirls, etc.), as though she's a long-time resident of the base and is on casual-to-intimate terms with everyone.
This led initially to art being drawn of Gotland being an honorary starter shipgirl, or as a 'waifu character' with childhood-friend vibes. This soon rapidly mutated into Gotland being depicted as outright brainwashing the Admiral (and other shipgirls) into believing the above, then evolved further into Gotland being treated as a reality-warper or time traveler with the ability to alter history to turn herself into an actual starter ship (or childhood friend/mother figure).
A likely reason for Gotland to act so chummy with the admiral is that Swedes generally speak very informally with each other, even with those of higher rank or status than themselves, such as their bosses. This is true even in the military nowadays. Unless you're speaking to royalty, speaking formally is often done to be condescending or for humorous effect. So it makes complete sense for Gotland to speak so informally with the admiral as to confuse Japanese players who live in a society where speaking formally is the default.
