When both Cobb and Ariadne go down to Limbo near the end of Inception, it's essentially the same as Cobb had left it. But if Ariadne went herself and hadn't heard about Cobb's limbo (so her subconscious wouldn't build it), would it be an ultimately different place?
Probably, as when the concept of falling into Limbo is first brought up by Arthur on the first dream level (the city, dreamer: Yusuf), he states that it is 'unconstructed dream space'. When Ariadne asks 'Well, what the hell is down there?', Arthur responds 'Just raw, infinite subconscious. Nothing is down there. Except for whatever that might have been left behind by whoever's sharing the dream who was trapped down there before. Which in our case, is just... (Cobb)'
This suggests that Ariadne would not have encountered Mal or the city she helped construct if Cobb had not been sharing the dream, should she have fallen into limbo regardless.