If I included my spouse in my extension, does she need to also file her own extension?

If you're filing a joint return, you don't have to file separate requests for extension. 

https://turbotax.intuit.com/tax-tips/tax-extensions/how-to-file-for-an-extension-of-state-taxes/L6FmvMk8E

Thank you for your response. Does that apply to federal extensions too? The link above refers to state extensions, so I just want to be sure.

It does apply to federal extensions too, you'll see that Form 4868 has a spot for your SSN (Box 2) and a spot for your partner/spouse (Box 3).

<a rel="nofollow" target="_blank" href="https://www.irs.gov/pub/irs-pdf/f4868.pdf">https://www.irs.gov/pub/irs-pdf/f4868.pdf</a>  

Thanks so much!