Background Info: My main character starts out the story with kind of a sad back story, it's not in a tragic way, just the normal kind of misfortune; losing family members, having to drop out of college (with a lot of debt) to take responsibility for her family's small business, and also losing all of her friends after she naturally breaks down from the stress and goes on a drug bender, they also felt uncomfortable that she wasn't in school anymore and stopped supporting her. I'd like to think that this is a common thing to have happen to someone, the story takes place several years later. She's fine, mostly happy, and engaged but still has a lot of anger and regret about how she handled things in the past.
My problem: I'm not really sure how to express that without having her have some kind of an annoying internal monologue or just seem pathetic. Her circumstances change a lot in the story and she has to come to grips with and let go of all of that negativity in the end.
Question: What is a good approach (or approaches) to depict her underlying anger enough to show that it's a problem, but also have her still be likable?
Hopefully I made this clear enough, let me know if you need more info!