Okay!! I emailed her and just got a response. Here's what she said.
Hi Lavonda,
I straighten my hair with a flat iron…I can’t think of the brand, but, It’s not one of those terribly expensive flat irons, in fact I bought it at Target for about 30 or $40 (It’s brown with pink titanium plates). I spend about an hour flat ironing really tiny sections…it’s a pain, but that’s how I get it super straight.
Tiani Jones