I would like to help you out here, according to me I don't think that there is a big difference in meaning between those sentences. Both are grammatical correct. And I think that they are interchangeable.
But can you give me a little bit more infomation please ? It's all about the context
I would use the ing-form when I want to stress the fact that I saw her coming. Especially when it has certain consequences that she is there eg: when she is big cheese
I would use the second option when it/she isn't that important. Just giving regular information.
But, if possible, please give me the context or discribe the situation.
Thanks in Advance