I do not understand the confusion over this. Why is she throwing tantrums? Because that is what kids do if they are allowed to and don't get disciplined for it!! She does realize that all kids try this, right?
Instead of "feeling sad when her daughter flips out" and worrying about the future where she sees her daughter getting worse and worse (which definitely will happen if she keeps scratching her head and feeling sad), she should discipline the behavior, so it doesn't get worse.
I have 3 kids who all tried these things and were not allowed to do them. Fast forward to the future, they are all happy well behaved kids I can take anywhere. Some needed more diligent discipline than others. But all are bright and caught on. They each tried to throw themselves on the floor and scream if I took something away or said, no. TRIED it. ONCE. Maybe a few times for my third ex hellion. But none of them kept it up when they saw they were only hurting their own butts after a calm clear warning by making that choice.
My third, who is now 19 months, tried blood curdling tantrums starting around age one. Now she has better self control than her two sibs who were never as difficult. She may point an angry finger at me, stomp her foot and hold her raging head high while tears fall (super cute) if I've (gasp) said "no" to her or something, but she does not drop, scream and spider kick anymore. It's all about discipline.
Her daughter is the perfect age to prevent these habits from cementing themselves. Firm consequence for tantrums. Every time. Clear rewards in the form of hugs and praise when she decides against the tantrums at a warning. Every time. She'll get it.
Simply not giving her what she wants will take WAY longer to sink in, because she is still being permitted to have the tantrum, which is what she really wants. And I have tons of friends who took the "ignore it" approach, and their kids are still tantrumming at age 5 and 6.
Pass her this site:
www.backtobasicsdiscipline.com