The extension gives her until October 15 to file --- if she is getting a refund you have three years to file and still receive the refund, but e-filing will close after 10-15.
That gives your spouse time to seek the W-2 from the employer.
W-2’s come from employers. There is not a federal or national website that provides W-2’s.
Some employers have payroll sites that will have your W-2. You might need to phone, drop in, email and/or snail mail an old employer to make sure they know where to send your W-2.
https://ttlc.intuit.com/questions/2561916-how-can-i-get-a-copy-of-my-w-2
Other ways to get W-2’s:
Pay Social Security $126 per W-2:
https://faq.ssa.gov/en-US/Topic/article/KA-02501
You can get a wage and income transcript from the IRS: It will not show the actual W-2, 1099’s, etc, but will show the income information the IRS received. It will not, however, show your state information. It will only show the federal information.
https://www.irs.gov/individuals/get-transcript