Highlighting the jealous part is very misleading.
The full text says that Ami was angry with herself for not handling it better because she wanted to be a better person. Also before Ami said the line the text describes Ami hating that Minorin is always so carefree. Also the text first said she had sympathy towards Minorin, then jealousy, then various others, and goes on to say Ami doesn't know what she wants and what to do anymore.
Sympathy here obviously means she feels sorry and knew that Minorin was and is going to go through a lot of emotional hardship, being caught in thinking that Ryuji/Taiga had something going so she burried her feelings.
Jealousy here can be interpreted - shippers would like to think that Ami is jealous of Minorin because of Ryuji's affection, but taking the full text as a whole and Ami's character it points more to the fact that instead of worrying about things and putting on a fake face like Ami herself is, she is jealous of the way Minorin handle things by that forward outlook. This is most apparent after the Sumire speech of herself being envious and wanting, but can't, be "a moron who only knows how to go straight forward". Ami was putting herself in the same shoes of Sumire and think that Minorin is the same type of straight forward people like Taiga/Ryuji who just confronts everything head on. She is jealous of the honesty of these people, which she, like Sumire, can't be.
EDIT: This is also what makes episode 4 (the "original" episode) a good episode in retrospect - it highlights this forward thinking aspect of Minorin which was never clearly explained in the novel.