Need Advice on changing name NOW ASAP

My partner is in a custody battle with her (husband). No one has been served with divorce papers yet. She cannot stand to look at or write "HIS" last name and apparently her legal last name.

1. She used her maiden name for her name on her telephone. She does pay it and will pay it, is this legal to use her maiden name NOW?

2 I was told that you can assume and use any name you want to, as long as you are not doing it for anything illegal, such as not paying the phone bil, to escape paying taxes, etc:. Is this true?

3. Does she have to wait until after the divorce to change her last name legally? or Can she change her last name NOW?

5. We both want to change her last name to MY last name. Does she have to change her name to her maiden name, either NOW or after the divorce?

6. Do we have to be legally married in order for her to change her last name to my last name?

Need legal, accurate, infomation ASAP, TY, Signed by both of us