I took a blood test when my ulcerative colitis flared up. My ast/alt level was about 65 and my platelet count was high. Is it high bc of the flare?

How high. Was your platelet count? If it is less than 1 million, it should not become an excessive clotting problem. Platelet counts that are slightly elevated are common in inflammatory conditions, such as uc flare up. Ast and alt levels are also affected by many things, but in this range it is usually self limited. Have these studies checked again in a few weeks at your GI doctor's office.
Probably. The slight increase in ast/alt may be medication related, but the thrombocytosis can definitely be related to stress response of acute illness.