SCT controller with minimal experience; influenced by a veteran; turned an air carrier inside a Cessna on approach to SNA that resulted in a loss of separation.

Narrative

I was the relieving controller. A C152 was on a 9 mile ILS final had been cleared for the approach. The relieved controller; during the two minute overlap; contacted SNA Tower for an early turn for Air Carrier X who was downwind abeam the airfield. It was not my intention to turn Air Carrier X inside of the Cessna. However; I let the controller lead me into it. My plan was to extend Air Carrier X downwind and I already had him slowed. Air Carrier X turned about a five mile base descending through three thousand feet. The Cessna was at 7 miles; I canceled his clearance and told him to maintain 3000. I turned the Cessna to a 270 heading; I should have used a 90 heading instead but I was concerned with the MVA. I gave traffic to Cessna; did not have time to give traffic to Air Carrier X. Cessna reported Air Carrier X in sight. I told Cessna to maintain visual separation. I am not sure but I think separation was lost prior to having visual separation. I do not think the MSAW went off either. Recommendation; do not let other controllers lead you into something you would not normally do especially if you cannot ensure separation. I think my plan would have been more efficient; Air Carrier X would have had maybe an extra ten miles to fly but it would have been safer for all concerned. As a new CPA we sometimes look up to the veteran controllers and heed their plans instead of your own.