When we say "imply" it means that we can be certain, and in this case we can't be certain. So it does not imply it is the same woman.
I eat an apple everyday.
Does not mean it is the same apple.
The apple example is unambigous. But your example looks much more ambiguous. It is possible to have nearly married the same woman on two occasions. The ambiguity could be used as a set up for a joke, but otherwise you should try to avoid it.
I almost married the same French woman, twice!
Or just add a clarification:
I almost married a French woman, twice. Not the same woman, of course. Two different women, first Marie in Paris in '94 and then Isabelle in Saigon in 2006.
If you are talking about person that you did marry, you would probably call them by name, not just "a French woman"
I almost re-married my ex-wife, Monique, in 2006. We'd split up two years earlier, but in Christmas 2005 we had an affair...