Playing in a friend's campaign and the other PC is difficult to play against, to the point that it's frustrating me both in and out of character.
The DM and I are playing a high-magic, god-touched struggle against good and evil where I'm having an amazing time living out my existential crisis, killing bad things and making life-altering decisions. The other PC however seems only vaguely attached to the plot, keeps making objectively terrible choices in game and pokes fun at my character every time she tries to open up and share anything. Basically, her character doesn't take anything seriously and doesn't seem concerned about the results of his actions.
Before I get into specifics, my question is is the tone problem something I should be fixing, or is it entirely on the DM to solve?
Our campaign's kick-off was that we were both dealt a half-deck of a highly modified Deck of Many Things, and our quest is to undo all the damage that's obviously caused. My character, Nasa, has multiple curses and stat penalties on her, her soul's been stolen, she has ghouls out for her blood, etc. Comparatively, the other player's character, Chirp, got 50k gold, a loyal companion, a couple of magic items and his only "problem" is that he has disadvantage against being charmed. It was 100% luck which cards we drew and clearly I got terribly unlucky!
Chirp is a happy-go-lucky guy who doesn't seem particularly interested in fixing his disadvantage problem. Comparatively, Nasa is a pessimist and a worrier, especially since all this bad luck has befallen her. She's determined to repent for her past mistakes and leave the world a better place, even if she has to die for it.
Nasa is (admittedly) pretty gloomy, and especially so compared to Chirp. Between the soul stealing and being marked for ghoul undeath she's accepted her fate as ever un-dead and is ready to martyr herself to help others. In trying to play her accurately it's possible I've made her too unpleasant to be around. However, I really have trouble dealing with Chirp when he's constantly mocking and belittling her.
Nasa believes she has magic (she doesn't) and every time she "casts a spell" Chirp calls her on it, tells her she's lying and tries to pressure her into confessing. He'll make fun of her attempts and belittle her for not actually having magic even after she stops defending herself. We had discussed the whole "not actually magic" thing ahead of the campaign and everyone thought it was hilarious at the time and was super into the idea, but now I feel attacked for it.
Nasa got paralyzed during battle and was left, helpless, with 3 HP since she'd been up close with the enemy tanking so the others could lay in hits. Chirp killed the enemy, but instead of making any attempt to help Nasa or even just protect her until the effects wore off he grabbed a handful of mud and drew a mustache on her face while she was frozen and nearly dead.
I figured it might help humanize Nasa to spill a little bit of her backstory, but in the middle of a halting explanation of some of her history Chirp interrupted and basically laughed at what she perceived as a personal sacrifice and cracked a couple of jokes.
I'm really, really good friends with both the DM and the other player. We've played other campaigns together (usually with me DMing) and while the player always chooses to portray a playful, goofy character something about Chirp is really driving me up a wall.
We had a session 0 where we discussed what the campaign was going to be like, and we all agreed to a heavier storyline. But this last session actually made me kind of angry because I feel like she's mocking my attempts at playing things more seriously.
I've mentioned my feelings briefly to both player and DM. The DM seemed concerned but hasn't done anything yet to fix it, and the player was moderately sympathetic but basically said something that sounded a lot like My Guy Syndrome to me - essentially that Chirp was just a naturally cheerful guy and not to take it personally.
I'm wondering if I've messed up in making Nasa and if I should lighten her up and give Chirp a reason to stay and get involved. This is my first time being a player instead of a DM. Is this tone problem something I should take upon myself to solve, or is it generally on the DM to fix such things, or even am I just reading too much into this?