To that same extent, most of her lines in the Season 4 episode "Go Far". To be clear, most of her lines are sung rather than spoken all while she's strumming her guitar.
Van accidentally mistaking Reba for Cheyenne while drunk and coming on to her, both of their reactions to the situation were priceless, and Kyra's comment about it is just icing on the cake: "So now you're my brother-in-law and my new daddy?"
Barbara Jean: Maybe next time I'll marry someone who's ex-wife appreciates me!
On Barbara Jean's new puppy:
Reba: You treat that animal like it can walk on water!
Barbara Jean: What is "dog" spelled backwards Reba?
(later on in the conversation)
Van Montgomery: GOD! It spells God.
Barbara Jean: Brock, I had an epidural. I think that's what Jesus would have wanted.
Kyra: I think that's what Mary would have wanted.
Later in the conversation:
Barbara Jean: (Looks at machine) Oh, look, I'm having a contraction. (In utter medicated bliss) Who knew?
Earlier, before she had the epidural, she's in labor while Van and Cheyenne are arguing over what college to go to. Barbara Jean attempted to be polite, but finally, she grabs Van by the stopwatch around his neck and yanks his head down.
Barbara Jean: I... NEED... DRUGS!
Cheyenne: You're leaving? Who's going to watch Elizabeth?
Reba: Oooh, that was close. I almost left her alone with her parents!
Van Montgomery: They all want grandchildren, but they never think of the consequences...
Van's "genius" duck call:
Barbara Jean thinks Brock is having an affair.
Reba: Don't think of it as Brock having a mistress. Think of it as us having a new girl for our club.
"Do it for our kids. Remember? The sweet ones that are blackmailing us."
Van's viral videos on Youtube in Locked and Loaded.
Van's rage during soccer practice in Bullets Over Brock.
Brock's complaint about Barbara Jean during a "couple's therapy" night in which the couples trade off.
"It's not just that we have to arrange forty stuffed animals every time we make the bed. It's that they have to be in a very specific order, and Blinky and Lou-Lou can't sit next to each other because 'they have history.' And you want to know what the sick part is, Reba? I Want to know what that is."
Which became a Brick Joke at the end of the episode when Brock stuck his head in the living room to inform Reba.
"Reba ... Barbara Jean told me the story about Blinky and Lou-Lou ... and it is so sad!"
It's actually two Brick Jokes in one. The therapist took one look at Brock and said he would be the first to cry.
The entirety of the episode where Barbara Jean thinks her house is haunted.
After Reba wrecks Van's beloved car Rhonda, Van's coping mechanism was to write poetry. Badly. Even eight-year old Jake thought it was bad.
Rhonda, Rhonda... A car I was so fond-a... I wish I could fix you... with a magic wand-a.
Later on, when Reba apologizes, Van snaps, "Well, thanks to you, I have to go and rent a Honda." (Van looks up, realizes it rhymes, and promptly starts writing it into the poem.)
The entire episode ("The Blonde Leading the Blind") qualifies, from Barbara Jean stuffing a peanut butter sandwich in Reba's mouth to prevent her from eating a sponge, to Barbara Jean's artistically-liscenced interpretation of Reba's apology in her diary.