I think you can apply together based on what they mentioned in this link.
http://www.uscis.gov/working-united-states/temporary-workers/employment-authorization-certain-h-4-dependent-spouses
"For your convenience, you may file Form I-765 with Form I-539, Application to Extend/Change Nonimmigrant Status, or with both Form I-539 and the H-1B principal nonimmigrant’s Form I-129, Petition for a Nonimmigrant Worker. However, USCIS will not process your Form I-765 (except filing fees) until after USCIS has adjudicated your Form I-539.
The 90-day period for adjudicating Form I-765 filed together with Form I-539 does not begin until USCIS has determined whether you are eligible for the underlying H-4 nonimmigrant status, whether your spouse is eligible for the underlying H-1B nonimmigrant status, or both."