Rae i have been into various sports at a pretty competitive level, my fiance has been on a program i set out for awhile and is making some decent progress.
It basically involves 3 days cardio with one of those days being circuit training with weights and core strength exercises. Then 2 days exclusively for weight training.
Obviously doing 5 days exercise right of the bat might be a little extreme so she started with 3 days in the week which we bumped up-to to 4 days after 3 weeks and then 5 days another 3 weeks after that.
The goal with exercise i find is to make a long term program because eventually the body becomes resistant to continuing to make gains on the same program (very similar to AEDs resistance on same dose after awhile i guess

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Therefore, we chose a 20 week program. Every 2 weeks we will increase the intensity and a duration of the exercises. The weight training involved all types of core exercises such as using the swiss ball for sit-ups, press-ups, hamstring building exercises. Then we did some more hardcore exercises such as squats, dumbbell presses, and dead-lifts.
The cardio consisted of swimming (30 min to begin with), running 30mins decent pace which we increased and stationary cycling (40 mins). The cardio days were alternated between these 3 things so as tot affect the body differently each time and work different muscles.
In regards to losing your breasts you will notice some decrease in size as your body-fat decreases. However, weight training alone will not make you lose your boobs. Usually this is a sight misconception and its usually extreme cases which you lose your boobs such as women getting below 14% body-fat which is quite low for women. For the average woman i would not worry to much about this to begin with.
In terms of arm exercises - i would not focus solely in arms because even though arms will tone up i often find women are very concerned about losing the bingo wings (as they say in the UK) and this will only happen of overall body-fat is reduced, you cannot spot reduce fat at certain locations in the body and your genetics will determine trouble areas of resistant fat loss.
However, if you do want to focus on arms i would do 3 exercises for biceps, 3 for triceps and 3 for delts. I like to do 3 sets for each exercise and pyramid the weight and decrease the reps. Usually something like 16 reps 1st set, 12 reps (more weight) 2nd set, 10 reps (more weight) 3rd set. You can get yourself a basic weight training book to get accurate description how to perform each exercise. When my GF began weight training she thought she was going to become massive and look bulky, again this is a misconception, it as actually extremely difficult to gain massive amounts of muscle for women due to lack of testosterone, also we are looking for more volume and not maximum amount of weight. However, the final set should be about 70% of your maximum strength for that particular exercise. Toned muscle will develop through decent resistance with weights so try not to be to light and too many reps too. Its a fine line between going to heavy and too many reps - choose what suits your body and what you prefer.
Again i must say i have always found better gains in core strength training often involving simple body-weight exercises. This tends to lead to hard workouts and makes you very agile and strong. My GF finally was able to complete 3 decent chin-ups after training her core body for awhile.
Anyway, i hope this helps you in someway Rae. Good luck.