Fighting and then disappearing for long periods of time

I've finally gotten Tara and Drusilla acclimated to living together. Or so I thought! Things went fine for the first few days and then a week ago they had a fight. I don't know over what. I heard hissing and yowling and I came in and they were leaping in the air at each other. I clapped my hands and both took off in opposite directions. Neither came out for days. I searched and searched but couldn't find them. However when I would wake up in the morning I noticed the food was eaten and the box used so I know they were around. Two days ago Drusilla finally started coming out and playing again and Tara came out and played with her, they were both friendly and purring. Yesterday, another fight and now they are missing again.

I introduced them properly and have Feliway. Is there anything else I can do to stop their fighting? I don't want them to hurt each other, especially since they disappear afterwards so I'm not able to check them out. Is there a reason they disappear for such a long time afterwards? I can understand the immediate running and hiding but to not come near me or each other for days?

Let them get it over with. They're not likely to do permanent damage, and the disappearing started when you scared them by clapping, and maybe they just need to work it out. It would be good if they had at least 2 or 3 litter boxes, and ate in separate places. Females will fight, but not forever, and may end up friends in future.