Personally I think 165cm after 6cm lengthening is a very good height for a female and the risks to get to 169 don't outweigh the benefits.
But I understand however that every person has their own situation. An outsider looking at us potential LLers will call even us men crazy for wanting any height at all. It'll be incredibly hard to explain to the outside world how we feel about our height and why we are willing to cut our legs to be taller. Same applies to this Betz female patient. She probably can try to explain her own story and motivation but we are prejudice and won't be able see her own side of the story, just like normal people can't see us men's side of the story.
I think ultimately it is up to her to decide what's the right choice. Remember for regular society even 1cm of lengthening is considered batshiet crazy. She might live in a country where even 167cm is below average for females. Again, we don't know her story, and she may suffer from height neurosis even worse than any male suffers. We just don't know her side.
I will proceed by advising to be more conservative, as we have seen with unicorn, another female, that women break their bones way easier because of lower bone density so less is ultimately more and women grow bone slower than men as well. These are things to take into consideration before going for high cm like 8cm or 10cm.
I recommend 7cm max, but this needs to be thought out hard and all factors must be considered, and there is some good advice in this thread. But it is ultimately up to the Betz patient herself.