i don't get all this Nikki hate, she acts like most people would in that particular circumstance. Her boyfriend used all her money, she was able to borrow more from a friend, he pissed that away, so she decided not to ask that friend for more money, because it's pretty weird to ask someone for money that soon again. I'm pretty sure if most of you borrow several thousand from your parents/family, you'd probably feel quite ashamed if all of it disappears in a couple of days, no? I don't think any normal person would be back the next day saying 'oh woe me, I need more money please'.
She only returns when she legitimately has no choice left, and when she is at her most vulnerable, because she hopes that she can trust MC.