Idiom: to dig in (one's) heels; used as a verb
Jennifer: How is the wedding planning going?
Jennifer: That bad, huh? What's wrong now?
James: We can't agree on the music. I just want to have a DJ, but Natalie has dug in her heels on an expensive live band. She won't even consider any of the alternatives I suggested.
Jennifer: Just like she dug in her heels with that expensive hotel?
James: Yep, and I assumed she'll dig in her heels on some expensive flowers as well.
Jennifer: Well, it is her wedding day, so she wants it to be special.
James: It's my wedding day as well, and I don't want us spending the next ten years paying off loans!
Meaning: To "dig in (one's) heels" is a phrase that means to refuse to give in. This idiom is used when a person stubbornly refuses to change an opinion or action. In the example, James says his fiancé Natalie is digging in her heels about wedding options that are too expensive.
Unusual for an English expression, the preposition in this idiom can be moved to the end without affecting the meaning. The expression to dig (one's) heels in (with the preposition at the end) is also correct and has the same meaning.
Here is an example of that usage:
Michelle: How about sushi for dinner?
Greg: I don't want to go out. Can't we just order a pizza?
Michelle: Well, I wanted something healthier than bread and cheese. How about that new salad place? That's not far?
Greg: Can't you get a salad from a pizza place?
Michelle: Not a good one. Let's go out.
Greg: There has to be a healthy delivery place. Let me look online.
Michelle: Wow, you're really digging your heels in on delivery, aren't you?
Greg: I just had a long day, and I'd rather stay home.