Undyne stayed with the group heading back down into the undergroud, many thoughts filling her mind as she went with them. Frisk and her may have been besties, and Undyne may have been employed as their bodyguard, but there was one person that she was devoted to above all, even more than the father figure in her life. 

And that person made a freaky love robot. 

Why Alphys.

Why did you have to make a weird freaky love robot who pretends to almost kill Frisk and why does that crazy weird freaky love robot insist that it's creation was meant to impress the king in a long shot of getting him attracted to her. He wasn't even her type, and even with Alphys' glasses, she could miss the point of something or not realize that the STRONGEST COOLEST FISH LADY MONSTER WAS KINDA INTO HER AND THAT HER COOL LEATHER JACKET WAS PICKED OUT JUST TO IMPRESS HER AND SHE HAS A SUPER COOL ENERGY SPEAR AND A [color=007236]GREEN ATTACK[/color] FOR CRYING OUT LOUD NO NEED FOR [color=fff200]BLUE STOP SIGN[/color] BUSINESS OR ANYTHING.

Undyne was building herself up, and she needed to release some steam. Throwing spears left and right wouldn't have done anything but cave them in, so she just had to cool herself for now until she could find room to vent.