You should always pay people back if you owe money.
Jennifer borrowed some money from Tammy last week, said she'd pay her back in a week  and just got her paycheck today.
Jennifer wants more money in her account.
Jennifer pays Tammy back what she owes her and gets another job too.
Jennifer tells Tammy her job didn't pay her yet and to wait another week.
Tammy respects Jennifer and feels closer to her as a friend.
Tammy doesn't trust Jennifer anymore and reconsiders their friendship.