Well that depends on how you frame the event. If you act platonic and innocent and not make any moves or hit on her or be flirty with her, then yes, she will assume the gathering was a "just friends" thing.
If you act in a romantic way from the start (i.e. kino escalation such as hand holding, arm around shoulders, and maybe even kissing) then the fact it was a "date" will be implied yet unspoken. And if your "hangouts" lead to more serious things like sex or sexual things then there is no way she would think the hangouts are just friend things.
And that's really common sense. If you really think about it, even a proper "date" (labelled as such in advance of the event) in which you act platonic will also in time, retroactivley, be considered a "just friends" thing, perhaps leading to the dreaded "let's just be friends" line down the road once a move is taken (too late).
It's all in how you act, not how you label.
Labelling a gathering a romantic date in advance so that you feel more comfortable making moves or whatever seems like a crutch or training wheel. If she asks straight up what it is, just say it is what it is, though usually she won't ask that in advance (i've never had that come up that I remember).
ex.
Girl: is this a date? or what is this?
Guy: It is what it is. or its whatever we make it or its going to be a fun night.
And when she is analyzing it after the fact, she will judge it to be a date or non-date based on how you acted on it, not how it was labelled to her. If you make out with her or something, I don't think she will think "gee, I think it was a friends thing". If you acted like a tool and made no advances or progress then it shouldn't be a suprise if she thought of it as a just friends outing.