Preeclampsia with HELLP syndrome: This condition is characterized by the onset of hypertension and often proteinuria after 20 weeks of gestation, which can lead to complications such as HELLP syndrome (Hemolysis, Elevated Liver enzymes, and Low Platelet count). The patient's symptoms of feverishness, nausea, vomiting, mild transaminitis, leukocytosis, tachycardia, and mild proteinuria align closely with preeclampsia, especially considering the pregnancy context. However, the absence of explicit hypertension in the provided information makes the diagnosis slightly less clear-cut, but it remains a strong candidate given the other symptoms.

Pyelonephritis: Given the symptoms of feverishness, nausea, vomiting, and the presence of mild proteinuria, pyelonephritis (a kidney infection) is a plausible diagnosis. The leukocytosis further supports an infectious process. Pregnancy increases the risk of pyelonephritis due to physiological changes that can predispose to urinary stasis and infection.
Hyperemesis gravidarum with possible superimposed infection: Although typically seen earlier in pregnancy, hyperemesis gravidarum can persist and be complicated by infections or other conditions leading to the observed symptoms. The presence of glucose and mild ketones in the urine could support this, indicating possible dehydration and metabolic derangement.
Urinary Tract Infection (UTI): Similar to pyelonephritis, a lower urinary tract infection could explain some of the symptoms, especially if it has ascended to involve the kidneys. However, the severity of systemic symptoms like tachycardia and high leukocytosis might suggest a more severe infection like pyelonephritis.

Sepsis: Regardless of the primary cause, the combination of fever, tachycardia, and significant leukocytosis raises concern for sepsis, a life-threatening condition that requires immediate attention. Pregnancy can mask some signs of sepsis, making it crucial not to miss.
Placental abruption: Although not directly suggested by the laboratory findings, placental abruption is a critical condition that can present with nonspecific symptoms like nausea and vomiting, especially if there's associated bleeding. It's a diagnosis that could be deadly if missed, given its potential to cause severe maternal and fetal morbidity.
Acute fatty liver of pregnancy: This rare but serious condition can present with nausea, vomiting, abdominal pain, and elevated liver enzymes, similar to what is described. It is a diagnosis that must be considered, especially in the third trimester, due to its potential for severe outcomes.

Wilson's disease: An inherited disorder that leads to copper accumulation in the body, potentially causing liver dysfunction, among other symptoms. It's rare and less likely given the acute presentation but could be considered in the differential for liver enzyme elevation, especially if other causes are ruled out.
Acute viral hepatitis: Although less likely given the context, acute viral hepatitis could explain the liver enzyme elevation and systemic symptoms. However, the presence of other symptoms like proteinuria and the specific context of pregnancy make this a less likely diagnosis.