I'm sorry to hear of Melina's condition.
Most cases of decreased platelet numbers (thrombocytopenia) occur due to certain infections, drugs, parasites or cancers (secondary thrombocytopenia), or be an autoimmune-mediated event (primary thrombocytopenia).
In severe cases, which is what yours unfortunately appears to be, steroids are used in conjunction with immunosuppressive drugs such as cyclosporine, azathioprine or cyclophosphamide. As an emergency treatment, a drug called vincristine is often used to bring the platelet numbers up; this usually has a positive effect in about 3-4 days, while supportive care is continued (fluids, stomach
protectants). Antibiotic therapy (doxycycline) is used in case thrombocytopenia is related to infection, most of which are carried by ticks.
Unfortunately, the intestinal hemorrhage complicates the issue. In general, about 70% of dogs with immune mediated thrombocytopenia recover with steroid and other drug treatment. Excessive hemorrhage, however, decreases this number and worsens prognosis.
I would definitely add on doxycycline (antibiotic), a drug like azathioprine plus vincristine; this can improve chances significantly.
I hope this helps; please let me know if you have any other questions and best of luck!