Both my wife + me are self emp. I have a 401k account. Can we make a $5.5k contribution to my account in her name or does she need separate 401k acct?

Are you and she self-employed in the same business or are your self-employment businesses entirely independent of each other?

Your contribution to a 401K can be in your name only and on your behalf only.

If she is part of a business as self-employed she would do her own 401K.