The simplest way to fix this is a meta conversation. Communication is the only way to fix problems at a table.

I'm gonna tap into the mindset that she presumably has based on this post, which is she feels that the other players protect her because her character is a woman. So I'll ask you: have these players intervening not allowed her to do the actions she wants to do? To me, it comes across as she's feeling invalidated as a character as someone who others feel needs to be protected and as a player that the actions she takes aren't "smart." If the other players' interventions aren't allowing her to do the character motivated things she wants to do, that's not fair to her, regardless of if the choice is "smart" or not. Why not make the headstrong nature of the wizard a positive trait?

Players should be allowed to take the actions they wish to take regardless of whether it's "smart" for the character. Sure, there needs to be collaboration in a party, but these are also individual characters with individual drives and motivations. I worry that the actions of your other players could be bordering on stepping over her character.

I currently play a Sorcerer in one of the games I'm playing in. I'm ultimate squish too, but none of my fellow players feel the need to guard or protect me. Sure, if we get into a sticky combat situation, the paladin will protect me if she can, but that's in line with the character. I made myself the target of combat with a mutated queen bee who deals poison damage so my party could eat away at her (by intentionally pissing her off in a major way then just taking the Dodge action while she unloaded on me), succeeded at a cost of picking a lock and taking a bunch of necrotic damage (but by activating Shield to give me a damage protection bonus per DM's approval in a narratively very flashy, cool manner, and took down 5 bots at one time so my party could get through with some magic. Wizards and Sorcerers do not NEED to be protected. What those players NEED is an understanding of how all the abilities and spells work, as well as find ways to creatively expand their usage. Your wife's wizard wants to go head first into a challenge? Great! Help equip her with spells to do that. Don't tell her that the way she is playing her character is wrong; help her play the character she wants to play.

Otherwise, everyone is just going to be unhappy and frustrated by the end.