Krista Tesreau says people told her she was ''a little crazy'' to step into the high heels of whirling dervish Tina on ABC's One Life to Live because the role had already been popularized by Andrea Evans and Karen Witter. But Tesreau had gained soap fame as Guiding Light's sassy Mindy (1983-88), whom many saw as a Tina twin, and after just three weeks of taping, she's already feeling comfortable in the new part. The St. Louis-born actress, 30, who appeared on CBS' Silk Stalkings in between soap jobs, did have trouble tracking Tina's sexual high jinks. ''It's like she's been with everyone on the show,'' she says. ''I got the [''One Life''] bible to try to figure out all her relationships, and it's so confusing. I finally made it easy on myself. I just went up to people and said, 'On a scale of 1 to 10, do I like you or not?'''