Looks to me like she's damping off. How much are you watering? This could just be that the soil is soaked and the seedling wont take root. You can take it out of there, delicately as if this is the finest puntang ever, try to get it some air and then replant.
I like to let my little ladies get to the point of almost dried out before watering again. This way the roots can run down deeper.
I'm just a newb too so hopefully some of the pros will have mercy on you.