Well, at first glance it looks like you have the achievement “Just Don’t Ask Me to Spell It” on your level 70 Tauren Druid. That would have unlocked a lot of content for your alternate characters that your wife wouldn’t have access to.
So for that achievement she needs to complete the criteria Valdrakken, City of Dragons, Time Management and Big Time Adventurer. You can find that listed on the achievement page and the comments section usually will list the individual quests in order.
For her, she is on Nowhere to Hide. Your character is on the quest just before it, “A Message Most Dire”, which I cover from the quote below.
For Zaralek Caverns, “A Worthy Ally: Loamm Niffen” is a weekly quest, so she’d need to have world quests unlocked by completing the Breaking Ground storyline.
Same with the others, you both already started the quest line on those characters but she is currently on the quest Scars of Earth and Fire. Your character has the previous quest still in progress " Where the Flames Fell".
Story NPCs tend to move around or disappear based on the part of the story you are currently part of. It looks like you started a quest line where Alexstrasza moved to Tyhold. If you had the quest “To Tyrhold” you could just abandon that and she would reappear in Valdrakken, but you have progressed beyond that and both have “Aspect Power”.
You should be able to speak with her in Tyrhold, or complete that quest line to return her to Valdrakken.
Hopefully, that helps.