I suspect everything you need to know about this marriage is encapsulated in the LW's first paragraph. Wife had a horrible week at Burning Man while husband frolicked with a new Soul Mate. Did she happen to mention her misery while they were in the desert, or was he too busy to listen? Or is she the silent self-martyring kind who doesn't want to burden her mate with her problems? Maybe the horror had nothing to do with social abandonment particularly, and maybe LW would have been miserable even if her mate had been by her side the whole time. But at least then he would have been being a good friend. Good friends do not let each other suffer needlessly, or if there's really no way to help, they at least ensure that no one has to suffer all alone. It's one thing if you're a drunken college kid who gets left behind at a bar when all your frat or sorority pals have hooked up for the night. And it's not such a big deal if you and your husband spend a few hours at a party where one of you knows more people and ends up having a much better time. But a whole week of being left adrift in a crowd while your husband lives it up with his new infatuation? Total selfishness on husband's part and pathetically low expectations on wife's part. Open-mindedness, atheism, independence, etc. have nothing to do with it. Great conversations made up of palatable lies are a complete distraction. LW lets her husband treat her like crap, and this probably started long before Burning Man.

LW, this is very different advice than everything else you're getting here, but I'll respond to the aside you made about your musical interests, in case that is genuinely more important to you than you've let on in the letter. It may be inappropriate advice for you, but I offer it anyway, because if I'd been told to do this when I was young and depressed and poor, it might have sparked something for me. It also doesn't preclude any of the other stuff people are telling you about college, health insurance, etc.

If you are a decent enough guitarist that you can teach yourself Top 40 or alt rock radio cover tunes by ear (or w/the help of online tab), and maybe even sing leads or vocals on some, you may want to consider looking for a wedding band to audition for. If you have never played music professionally you may think this is an insurmountable goal, but I'd bet that even in a major music hub like LA there are mediocre party bands filled with weekend warriors and semi-talented wannabes who manage to get weddings and private parties that pay a few hundred bucks per gig. Or even crappy bar gigs where you'll at least get $30 cash and some free beer. Start out with a not-so-great band and, if you've got talent and can learn new songs quickly, you'll eventually find better outfits. At the very least, if you can muster enough energy and courage, there may be open jam sessions where you can play with some other people and help lift yourself out of depression a bit.

Advantages: extra money, a chance to improve your ear and your chops, and a chance to experience both the fun and the aggravation of being a pro musician--to find out whether it's a path you want to follow or just a childhood dream you need to discard without regrets. Also--even if you're playing cheesy songs a lot of the time--"Love Shack" or whatever--it really, really helps one's mood and outlook in life to make music for a bunch of happy, drunk, dancing people.

Disadvantages: cheesy music a lot of the time; it's a tiring lifestyle, it can be almost as humiliating as the law firm scene, and you will definitely see less of your boyfriend. It may also not be possible right away if you don't have enough equipment--guitar & amp & mics. Nothing fancy but needs to work reliably. I would check out the area's used music stores and pawn shops.

Also, in terms of your own songwriting: learning to play decent covers of even mediocre, overplayed pop songs REALLY helps with your own craft.

Nocal:

If LW and her husband have the resources to let her pursue her artistic ambitions in a responsible way, it's not even remotely related to something called "slacking"--nor is it, as one more polite but still misguided person put it, a matter of "taking time off" before motherhood. For those who are called to it, creative writing is incredibly hard work that requires vast amounts of fortitude and perserverance, especially since neither the corporate machine nor killjoys like you can understand the value of it. LW either is truly built to be a novelist, or she'll find out soon enough that she isn't and decide to do something else with her life. The way she has been letting her brother leech off her, the woman is obviously already guilt-ridden enough without being misinformed that her dreams are worthless.