My friends new husband has just left her for a previous 'baby mama' less than 1yr after their vows. She has 1 child, 4yrs, with this man. He not only left her, we believe he was having and affair for the last 2mos with this ex. Is she on the hook for the divorce or can an annulment be obtained in a quick fashion?

Since there is a child involved she will need not only a divorce but a child custody and a child support order from the court.

She will have to get an attorney ( or legal aid) and file. She can try and make him pay for it.

This will not be quick unless he just agrees to the child support, the visit issues and the divorce and the separation of property

Knowing where your friend lives and her husband would be helpful.

Generally speaking annulments require specific grounds be established such as fraud, bigamous relationship, things like that. It is not enough to simply say "it didn't work out" or "we were only together a few days and he left". There's an urban legend going around (much like the one about common law marriages, which only exist in a few states now) the if you were only married a brief time you can get an annulment and that annulments are cheaper and easier. It's not true. It can often be easier and faster to simply file for divorce if you are in no-fault state.