she looks a bit tall and stretchy to me.. what kind of light are you using (if any)?
If she's just standing in the window, then this can explain it as well, as the amount could be on the lower side (depending on where you live) and low intensity of light makes plants stretch for it..
that the cotyledons are yellowing and dropping off is normal so don't worry about that..
are you giving any nutrients? If not, then at this point you should definitely start giving her light veg-nutrients (but don't overdo it, and slowly raise the amount over a few weeks).
happy growing