I would need more information really.
Often times I "worst case scenario" a situation, so I might say 1:35, thinking most likely I'll be there by 1:20 but I'm building in a cushion.
Also what was the reason for her lateness. If it was unexpected traffic, its out of her hands (and applies to the above situation - traffic might clear up and thus speed her arrival), vs if she left late and is just being casual about time, vs and emergency cropped up. Was this an important lunch is another factor.
I do think as a base, asking someone to wait 35 minutes is not cool, but there are situations where its less of an imposition then others.