Humm. I would try syringing doses of Rejuvenaid into her. If she’s not eating much solids, she definitely won’t eat this willingly, but the rejuvenaid is liquid vitamins and minerals and is formulated specifically for pre-weaning age foals, so she’s right in that age-group and she needs the nutrition. You know it’s doing something good when they start getting feisty again. Otherwise, I second the idea of trying to get her to nurse off an Igloo and to try different brands of equine milk replacer.
You start by bottle training them and if you have a mare that is still lactating you can milk the mare (you can induce any mare to lactation pharmaceutically). This teaches your orphan that the bottle tastes like mommy’s milk and it is more appealing to them. Then, you start introducing the Igloo with as much of the mare’s milk in it at a time, and then start mixing a bit of replacer in with the mare’s milk, starting small, 90% mare milk to 10% replacer (you’re introducing a new taste here) and then gradually raise it to 50/50 when the foal is getting vigorous and enthusiastic on the Igloo, and then gradually increase it to 75% replacer to 25% mare milk. It’s a bit of work at first, but I think we need to take a step backwards and treat this foal as if she were still about 6 weeks, because as you say and have noticed, this loss has really flattened her. This might be the only way you can perk her up. Young babies need not only the nutrients in mare milk, but also the fat, calories, and protein for proper growth. She’s only going to get this from milk until she can do more than just nibble on solids.
And the idea about yogurt - it’s sounds unbelievable, but it’s true, they do like strawberry yogurt, sometimes some prefer raspberry or blueberry better.
The EZ Milker makes milking a mare as sweet and easy as banana cream pie.
Otherwise, jingles and sorry for your loss.