I'd keep the forced feedings up for a while. She'll probably let you know when she doesn't need them any more. If you offer her your egg yogurt mash and she seems uninterested, then force it. A few hours later, offer it again. If she seems uninterested, force it. Keep this going every few hours. Hopefully she'll develop an appetite soon enough and you won't have to force it.
This reminds me of when I'm sick, REALLY sick, like stomach flu. After not eating for so long, it becomes hard to eat. There is no interest. If somebody didn't make soup and bring it to me and tell me to drink some, I'd starve all day. And my illness would last twice as long. It's this way for anyone, especially those that live alone. At this point, your hen is like someone living alone, and she can't care for herself, so you need to force the nourishment in her. Just like when YOU are sick, and your body needs small amounts of nourishment all through the day to regain some energy... Soon enough, hopefully, she'll be in your cupboards rooting around for crackers, or asking for a Happy Meal.
Small amounts, many times a day.
Increase the amounts as she gets more willing to eat.
Is she still outside?
I don't know why but this whole time I assumed you had her in your house in a cage or box.
If she isn't, you might consider it to make feedings easier. But that's up to you.