James:

Quidditch, the amount of pranking he does which then leads to many detention and his slight flirtatious manner with Lily.

Sirius:

The amount of time he spends with James over you, his charming ways (sometimes you are insecure about him with other girls around) and the way he talks to Slytherins.

Remus:

His ability to put himself down and isolate himself from others which leads to you being over affectionate (when the full moon is coming, he isn't particularly fond of affection and becomes irritated if there is too much).

Peter:
Both of your insecurities. He always wants you to see how amazing you are but can never let you in enough to see his own good qualities. And you always try to get him to see what you see in him.

Regulus:

His prejudice against other houses and those who aren't pureblood and how are arrogant he can be when he is with his friends.

Lily:

Her friendship with Snape, how you act when he is around and her friendliness with James.

Marlene:

Food (you both are very possessive over your food and don't like to share, quidditch and the way the other seems to check out other people.