Cat is vomiting frequently, any ideas on what might cause it? Or what to do?

My cat Leloo has been vomiting frequently, usually once a day or more. Most of the time it looks like she's just regurgitating what she eats. And other times her vomit is runny with mucus. There is another cat in the house, so we initially thought she was eating too fast due to territory issues. So we separated feeding areas to allow both cats to eat in private. This has not helped. She has lost some weight and her appetite has decreased. But other than that she has no other symptoms other than being more affectionate than usual. She is not running a fever, there is no tenderness or pain in the abdominal area, and she seems to be acting like her normal self (not including the vomiting and decreased appetite). I feed her Purina one sensitive systems and give her a hairball reducing treat daily. All the local vets are closed till Monday any ideas of what might be wrong or what I can do?