A half-pood (8kilo) 'bell is usually suggested for small folks/women.
More important is learning prober technique. DON'T 'just grab' a kettlebell and try to follow some DVD. Read and/or watch instructional material from
Whatshisname at Chronicles of Strength.
Take the time to know what you are doing before you plunge into anything. All these people, and many others, have simple progressions for learning to swing the kettlebell productively and safely.
While the kettlebell is hard to beat for metabolic conditioning (much more intense than rope-skipping with no impact) Bodyweight work for strength is a very good idea. You can find good progression schemes in 'Convict Conditioning' by Paul Wade and 'Primal Blueprint Fitness' by M. Sisson etc.
A few minutes of strength work followed by 10-20 minutes of kettlebell intervals will do wonders, IF you are patient and careful at the start.