Forcing your daughter to eat starts a cycle of power struggles. It could be that her not eating now is the result of your anxiety about her not eating. Or she could have a medical condition causing her to not eat.
I recommend backing off from the food issue. Put a piece of bread and butter by her bed so that she can eat in the middle of the night without waking you. Bread and butter is the way my mother, and now me, evaluate whether or not the child is really hungry. If they are they will eat the bread and butter.
You could also try letting her watch a video while she's eating. Her mind will be occupied with the video and she may forget that she's rebelling if that's the issue.
I would first take her to the doctor since stomach pain is what awakens her and she got up in the morning very pale and nauseous. There are other reasons for pain than hunger. There are health reasons for being pale and nauseous. She may be not eating because of a medical condition. One possibility is that her blood sugar gets low and so when she eats she feels better because eating raises the blood sugar level. I get pale and nausous when I go too long without eating but my stomach doesn't hurt. (There is a difference between the way our stomach feels when we're hungry and when something is wrong. I have felt both kinds of pain.) I try to eat something before I get pale and nauseous. She may need a snack in the middle of the night. She may need to eat smaller amounts more often. It is important to have the doctor evaluate her health soon.
My grandchildren sometimes eat very little at dinner time and I don't think they have awakened in the night because of hunger. They do not complain of pain either. They say they're hungry at bedtime and when I'm there I offer them a piece of bread and butter. Only once was it accepted.
It is very important to rule out a health condition. At the same time it's important to take the pressure off of eating or not eating. People, especially babies and preschoolers, will eat enough unless they have a health problem. Their appetite comes and goes. Sometimes they eat second of everything and other times they eat very little. This is normal. What causes me concern is the combination of pain, paleness and nausea.
If she doesn't eat because of not wanting to stay at the table you are in the midst of a power struggle. You can change this by ignoring how much she eats and making the rule that everyone stays at the table until everyone finishes eating. Or you could say that everyone stays at the table for a set period of time. Perhaps 30 minutes. This takes the struggle away from food and onto the real issue of staying at the table. She will test these boundaries. You will need to stay firm. When she leaves bring her back to the table in a courteous manner. Kids like to see parents angry because anger proves they have power.
Power struggles are a whole other issue and I've already written a book. :):) After writing this answer I looked at the website you cited. Please go back and read it again.