Assuming an average woman... a.k.a
NOT already strong or very much in-shape for their chosen sport... And following the following training plan:
First, get strong with a simple beginner barbell strength program.
The foundation of the routine would be the big compound lifts: squats, deadlifts, presses (bench and overhead), pull-ups, rows, dips, snatches, power cleans, clean and jerks.
To that list of fundamentals, add farmer's walks as a buttress for the squats and deadlifts in developing a strong posture against heavy loads.
Use Barbells for getting strong, with dumbbells a close second. Kettlebells work well for combining strength with conditioning, but they don't provide the really heavy stimulus that makes squats and deadlifts maximally productive.
After strength
Once she's strong enough, she focuses on power and sport-specific strength. She has already incorporated power work in the form of power cleans quite early in training. Now she prioritizes more power exercises because she has a strength baseline.
Her program for a moderate medium-term set of strength goals would roughly look like a double bodyweight deadlift, squatting bodyweight ten times with ease, a dozen strict pull-ups, a bodyweight power clean, and so on.
Sword-fighting-specific work, may involve rotational work, farmer's walks, more sprints, snatches and jerks for power development, barbell complexes or 20-rep squats for strength-endurance, unilateral work like lunges and pistols, gymnastic feats... she would benefit from being capable across a range of strength movements, so once she is strong, she may cycle through variations of basic movements in order to become familiar with a wide range of athletic movements. For example, cycling between back squats, front squats, loaded pistol squats, and Bulgarian split squats.
For both speed, conditioning, and power, she would do sprints and interval running. For power--which also benefits speed--she does the power variants of the Olympic lifts: power cleans, power snatches, jerks.
As it may be hard to challenge her conditioning during skill work, she may incorporate conditioning in addition to sparring, or perhaps she may get plenty of conditioning just from rolling.
If that was the case, perhaps because of a surfeit of technique work instead of sparring, then she may perform something from this cornucopia of conditioning options that is too numerous to fully list.
For example: cycle through a moderate variety of power-biased conditioning workouts (such as kettlebelling, tire flips, sandbag complexes, Prowler pushes, and sled drags) and occasionally return to benchmark workouts (e.g., "how many 24kg kettlebell clean-and-jerks can I do in ten minutes?") to gauge progress.
The Question:
How long would it take ON AVERAGE to get to the point so that she can:
Fight while wearing really heavy armour. The helm itself can weigh up to 2kg, the mail can weigh up to 12kg. Add the gambeson and plates and you end up with around 20-30kg.
And have the anaerobic capacity to do 1 minute of really intensive swordfighting with a single handed sword weigh around 1.2kg.
Plus have superb control over her blade at all times.
With the strength to knock another armored knight to the ground.
Assuming that she is devoted to being that good.
Sources:
https://fitness.stackexchange.com/a/11677/15433
Making a training plan for medieval swordsmen / reenactment
Does this even belong here? Or perhaps on one of the other fitness-oriented sites, 'cause this site doesn't seem to be about HOW long it takes, but more WHAT it takes...