1. Meeting her, I will be very glad.

2. When I meet her, I will be very glad.
3. If I meet her, I will be very glad.
4. As I meet her, I will be very glad.
5. As I will meet her, I will be very glad.

(Are they all the same? Which one is correct, #4 or #5?)

1. is wrong, because "Meeting her" implies past action.

2. and 3. are good

4. and 5. are not usually considered standard English.