Cathe tells what weights she's using as a guideline, not as a recommendation for everyone to use. Most definitely start lighter! Jerking the weight will lead to injury and may also train you to use bad form (which will make further injury more likely). Using too heavy a weight will also mean you are probably using muscles besides the targeted muscle to move the weight (ie: using your back--an injury waiting to happen--or your shoulders on barbell bicep curls).
It's much safer and effective to go a bit "too light" at first with good form than to go too heavy with bad form. Actually, in one of her earlier weight workouts (PS?), Cathe didn't say what weights she used, and later posted on the forum about not wanting people to take them as a recommendation for what they SHOULD use. After many requests, she went back to saying what weights she uses. Start light, focus on form, and work your way up. Some day, you might even be able to lift heavier than Cathe! Or maybe not. It doesn't matter.
You can still use them as guidelines. For example, if you know that you lift about 1/2 as much as Cathe for bicep work, and for a specific exercise she uses 10#, you might aim for 5#. It's a good idea to write down the exercises you are doing, and the weights you are using (and how they feel to you--too heavy (were you using bad form, or could only do 1/2 of the reps?); too light (could you have done several more reps easily).
