She was introduced as a very unreasonable teenage brat in Honor Council, and what's worse not only does she mock Josh for being not as intelligent and physically skilled as her, she embarrasses Drake in front of people, by showing his notebook and even showing what he really thinks about Mrs. Hayfer, and what's even worse is she didn't even have permission to touch Drake's notebook.
She was a bit unlikeable in "Mindy's Back". She initially dumped Josh, just because he won't tell Drake that Josh is dating her, causing Josh to feel a bit anxious of what his stepbrother would think that he's dating the person that he really hates, and when Josh told Mindy that he never actually told Drake because he'd feel a bit embarrassed, they do get back in the end however with Josh telling that Drake was perfectly cool with it, but here's the thing: Don't force a person to tell about your relationship status, be patient if he/she wants to hear about someone's relationship status, then say it properly.
She tends to be an over-competitive and irritating person towards Josh, even rubbing it on his face, and what's worse is she still does it when he was in a relationship with Josh or the time of their initial break-up.
As stated in BQ #1 she's a teenage brat, Mindy was responsible for pulling the prank on Hayfer by parking the car in the classroom, and when she revealed that she did the prank to Alice, not only did she raise her voice towards her for giving her a B, she also mocked Josh of why he's a neanderthal and how she so much superior to him.
She still hates Drake, for no absolute reason, it's clear that Drake doesn't hate her that much after finding out that Mindy is dating his stepbrother, however she still hates him for an unknown reason is it because he lacks common sense, is it because Drake usually drags Josh in flabbergasting situations.
She made a deal with Megan to shave Josh's mustache, which just sounds really stupid, if you wanted to shave his mustache so badly then why didn't you do it in the first place, by sneaking in Drake and Josh's room after midnight, and if Drake wakes up hide in an unnoticeable area, if he gets suspicious it doesn't matter since Drake sometimes doesn't have common sense and needs Josh to back him up at times, and she even complains that Megan is $15 short, well it's your fault for making a deal with her.
She was a total idiot along with Josh in "Eric Punches Drake", well it was Drake's fault for why Josh got jealous of the guy Mindy's been hanging out with, but still why did she have to make things worse by turning Josh's slight jealousy into a bitter one, and what's worse is Mindy even rubs in how that guy met Oprah Winfrey in front of Josh's face.
Despite having an on-and-off relationship with Josh, she's still a pretty nice girlfriend and would do something nice for him such as letting him win in a science fair since she really feels bad for him and doesn't want to see him as a loser anymore stating that she kinda threw away her over-competitive nature.
She does have a lot of funny moments, such as making really confusing faces at the time when Josh met her parents, and usually when Drake starts calling her names with Mindy having one for him as well, and the time where she really tried hard to convince Josh to shave his mustache.
She does slightly improve during the run of season 4, showing her much more mature, less competitive, kind-hearted, friendly nature and finally discarding her bratty personality.