If you cannot have access to her "finances," how did you prepare a joint tax return? You would need her W-2s, 1099s, and other financial documents or information.

I'm not sure exactly what you mean by "signing the tax return on TurboTax." If you are e-filing, you each "sign" the tax return by entering your 2020 AGI, which is the same for both of you if you filed jointly for 2020. There is no written signature on an e-filed tax return.

There is no way to give someone limited access to your TurboTax Online account. If you give your ex access to the account, she can do anything that you could do. What I would suggest is that you send your ex a PDF or printed copy of the tax return for her to review. That way she cannot change anything. Have your divorce lawyer prepare a document for her to sign, authorizing you to electronically "sign" the return on her behalf for e-filing.

getting a signed document from your spouse is vital for you. it is a serious violation of the tax laws to file a joint return unless both consent. that signed document protects you from your spouse later denying approval was granted

@linespecialest34 why would your ex authorize their signature without seeing the entire return?  

if you two are consenting to file Married- Filing Joint since you were not divorced as of 12/31/21, then consent is consent.  

alternatively, you both can file Married - Filing Separate.  It's not a problem.  Then the ex doesn't have any right to review your return.  More likely the tax each of you pay by going this route will be higher, but if there is something you don't want to ex to see, that is the cost of the ex not having full access.  Each of you has the right to file in this manner.  (but if you go this route note that you two must both either take the standard deduciton or both itemize - you can't mix and match).

Also, you may want to discuss filing joint with your divorce attorney.  Even if both parties agree to sign, who is paying the tax that is due? who is getting the refund? how is that going to get agreed to?  what happens later if something was missing or the IRS audits. 

You have both gone your separate ways, why the would you want to file Joint??????  Talk to your attorney!!!

Did you live in a Community Property State in 2021?

" Is there a way that she can just review the tax return and sign it on TurboTax without gaining full access to TurboTax so she doesn't try to change anything?"

No.  If you give her your login password, she will have access to everything.  If she agrees to file jointly, I suggest you print the return, get it signed in ink, and file by mail.  That's really the only safe way to prove that she agrees to the filing, and would prevent her from claiming fraud on your part.

This is something that should be handled by your attorneys.