This summarizes the conclusion; whether faithfulness is virtuous depends on whether the faithfulness is directed towards something praiseworthy. If something is virtuous, it must be praiseworthy. If it isn’t praiseworthy, then it isn’t virtuous.

This is premise. It explains why only something praiseworthy can be virtuous, which supports the conclusion that the virtue of faithfulness depends on its object (i.e. whether the object is praiseworthy).

This is a premise. It’s part of an example that demonstrates why faithfulness is not inherently virtuous: because the object and/or behavior of the faithfulness may not be praiseworthy.

The argument isn’t concerned with drawing a distinction between faithfulness and resentment. The author acknowledges that resentment is a type of faithfulness, but doesn’t discuss similarities or differences any further.

The author doesn't make this claim. She states that resentment isn’t considered virtuous, but doesn’t discuss whether it should be; there’s no judgment, it’s simply presented as objective fact.