In a medium bowl, whisk together the garlic, honey, Dijon mustard, grapefruit juice, balsamic vinegar, olive oil, salt, and pepper until emulsified.

In a large salad bowl, combine the fresh baby spinach, grapefruit segments, diced avocado, toasted walnuts, and crumbled feta.

Drizzle the dressing over the salad and gently toss to coat without bruising the ingredients.