Brent asked, yeah, but tons of other guys asked too. so why Brent in particular ? the one guy MC hated the most, and that picked on MC constantly... there were other guys, decent guys even, guys that shared her interests for sure, MC is not the only nerd. and she
stayed with him despite all his BS. her dating brent is just a plot device, at this point.
Dude, she ghosted MC for three months. you can be embarrassed and even awkward about some stuff with your friend, but MC was her best friend, and she began to realize her own feelings too. and the excuse of losing her phone can't work, she got another phone, and she knew where MC lived. even if she didn't want a handout to solve her problems, going to see him and talk about what is happening to her, and about the confession, is the least she can do.
She wanted to fix her problems herself, sure. but she could fix them while still being in contact.
if you ghost your best friend overnight just after they confessed, you send a very clear and devastating message. she is supposed to be a character that cares about the others before herself, with a good amount of empathy, but in the one instance where it mattered and with the one that should have mattered most, she couldn't call upon her inner traits and qualities ?
Just to be clear, I like Nicki, and her character and story. but there are still plot holes that need addressing. and she needs another boost in growth.
She is the only character that MC can really be sure of, 100%, like you said. though she have limits too as we can find out in her dark path.
When you reach new thresholds of wealth, you open your mind to new "wants" as before you didn't allow yourself to consider them without the means. it's like when you're dirt poor, you focus only on survival, food and essential items. but when you get decent incomes, entertainment comes into the picture.