Marissa

I'll do the first, but want to point something out about the second--

Mom was in a tizzy. As always.

Bending down to window height, Alyce pressed a kiss to her mother’s forehead. “We’ll be fine, Mom, honest. Go on your trip and have fun.”

Is this the start of the chapter? Okay, I'm just done grading more than 1000 essays, so I'm more comp-minded than I ought to be with fiction. Bear with me! It seems like you make an assertion-- Mom was in a tizzy-- but there's no evidence to support it. If it's just a thought in Alyce's mind, what's made her think that? I'm not sure you need anything, but let me just point that out as something to consider. I know you probably want those short lines as a hook, but they really sort of function like that unattributed dialogue Theresa and I are always decrying. (And if this isn't the start of a scene, never mind, to quote Gilda Radner.) We don't know who thinks that or why. Think about ways you can insert a bit more context as you go on. Like here:
Bending down to window height, Alyce pressed a kiss to her mother’s forehead. “We’ll be fine, Mom, honest. Go on your trip and have fun.”
I'm sort of wondering what "window height" is. ? Car window? I know setting up a scene is unfashionable these days, but if this is the opening of the scene, at least tell us that she's bending over a car, so we don't assume she's 8 feet tall. :) "Car window" is a quick way to do that.

Consider starting with some evidence that Mom is in a tizzy, calculated to let us know when and where this is taking place. Just an example: Her hands were viselike on the steering wheel, but her frantic face was sticking out of the open window.
Bending down to window height, Alyce pressed a kiss to her mother’s forehead. “We’ll be fine, Mom, honest. Go on your trip and have fun.”

Be physical here. What does this feel like? We're in Alyce's head. Is her mother's forehead sweaty? Clammy? Feverish? Hot from the sun coming in the windshield? Just look for modifiers that can slide in information.

“Well… don’t forget to call me every night. I want updates on what you girls have been doin’. Get your homework done, and no parties please.” Mom leaned out her window and looked back at Jenni who was fighting to pull a small suitcase out of the car. Her Texas drawl increased with every other word. “Jenni Hart! I’m talkin’ to you. Please listen to me when I am speakin’!”

Now here's a point of view thing. It seems like you're switching to Mom's pov here, and I know you're not. Put Alyce back in there--
Mom leaned out her window and looked past Alyce at Jenni who was fighting to pull a small suitcase out of the car. Her Texas drawl increased with every other word.

Or something like that. Block your action. Alyce is standing next to the car, right? She's just bent to kiss her mother. Then Mom starts yelling at Jenni. Alyce is still bending there, lips on Mom's forehead? No? Then tell us she straightened up, or that Mom pushes her away so she can yell unimpeded.

I got confused about why Jenni is removing a suitcase from the car rather than putting it in. That's because I have no clue if they're still at home and seeing Mom off, or if Mom is dropping them off somewhere, hence Jenni has a suitcase. How about "her small suitcase"? That at least makes it clearer that she's not taking Mom's suitcase out for some reason.

I know it's really hard in openings to get everything in-- but don't let the reader be confused. Find out what's confusing-- what misconceptions the reader has-- and revise to fix them. This is a good start because it sets up two teenagers (I assume) alone in a house and somehow I think Mom saying, "No parties," might be observed more in the breach. :) Just make it clear where they are-- their own house? Their dad's? Somewhere else?
Alicia