>>“Amber I'd like to talk to you about your attitude.”<<

That needs a comma after "Amber."

>>You are the one who is making mistakes with giving girls jobs they can actually cope with. <<

Was that supposed to say "they can't" above?

>>“Think about it Jaya. <<

That needs a comma after "it" above.

>>Unhappily, she pulled her hair into a ponytail before going to join her group.<<

Vague antecedent. Replace "she" with "Amber" for clarity, since other people were mentioned right before this sentence.

>>“Hey Amber,” Steph said<<

This needs a comma after "Hey."

>>Steph had actually tried to convince her to focus as back-up but as that was the job that killed her father she had avoided it at all times.<<

This would benefit from commas:
"Steph had actually tried to convince her to focus as back-up, but as that was the job that killed her father, she had avoided it at all times."

Also, "all times" is misleading, since Amber has done back-up and is about to do it again. Maybe change this to "she preferred to avoid it" or "she had avoided it as much as possible" instead.

>>“Can I talk to you Amber?”<<

This needs a comma after "you."

>>Everyone else seems to know where all the traps are and the quickest way to get where they need to go, but I know nothing about the house at all.<<

Wow, this is a splendid way to show-not-tell that this girl is unready for the job, and their leader is an idiot.

>>“You're going to Christophe's library right?”<<

This needs a comma after "library" above.

>>Going into Christophe's library without being at least adequate at magic was dangerous to say the least but they'd never had magic tests so Jaya would have had no idea, if she really was working from the test results.<<

This is long enough to be confusing. It would be more clear if subdivided, perhaps like this:
"Going into Christophe's library without being at least adequate at magic was dangerous to say the least. However, they'd never had magic tests, so Jaya would have had no idea, if she really was working from the test results.

>>Holding her hand out for the map she thought carefully about the safest route for Kenner. <<

Vague antecedent, because Jaya was just mentioned but this is about Amber. The simplest fix would be "... the map, Amber thought..." A clearer version would be: "Amber held her hand out for the map, thinking carefully about the safest route for Kenner."

>>“When you walk in the door turn right. <<

This needs a comma after "door" above.

>>It was a sticky dark that clung to everything. <<

This is a really interesting image. It made me wonder if the darkness spell would actually get on people, like molasses, and need to be scrubbed off later before they could interact normally with light again.

>>Without stopping to think she aimed straight for Christophe's library.<<

Vague antecedent. Change "she" to "Amber" above.

>>Amber focused on her wand again and tried to get at least one of the jewels to light up. If she could see something, anything, then that would be an achievement.<<

Tch. Better to sidestep the blockage and hang bells on the beast.

>>Carefully, not wanting to be bitten again, she put her hand out to find which of the two is was. <<

That should say "it was."