non-separate entities

i am one half of an increasingly insane relationship. again. but here's the thing: she's one of my sisters, not a significant other.
we're sharing a room this summer and planning to move into an apartment together early next year (more on that another time). and because right now i'm not working and she has an irregular schedule, we've been spending a lot of time together both in and out of the house. things have gotten to the point where when one of us says "we," everyone knows who we're referring to; and people sometimes address us both even if they're only talking to one of us.
and let me tell you, internet, it is FREAKY AS SHIT. i wonder sometimes what sort of effect my relationship with her will have on the rest of my social life, because we go out together so often that i think the staff of the area restaurants think we're dating. i know, hilarious.
but sometimes it really does worry me, because sometimes we kind of function as a unit. am i losing bits of my identity like this?