how can a woman can have twins from differents fathers ?

IT is possible.

Odds are slim though!

It happens when a women releases two eggs a month and has sex with two different guys in a short period of time. The two different eggs get fertilized by the different men's sperm.

It happens when a woman produces two eggs at the same time, then has sex with two different men, usually within a day of each other. The medical term is Heteropaternal superfecundation

Here are some cases in which this has happened:

http://www.today.com/id/30864533/ns/today-parentin...

and

http://www.theguardian.com/lifeandstyle/2011/aug/1...

In addition, it sometimes happens that a woman continues to ovulate after becoming pregnant (rare) and gets pregnant a month or two after conceiving her first child. This would most commonly be with the same father, just another example of how twins can be conceived at different times. It is called Superfetation http://en.wikipedia.org/wiki/Superfetation

In 1989, Marty and Drew DePietro, conceived 3 weeks apart, were born in Sudbury, Ontario, Canada to Dean DiPietro and Carmen Lafond. They were born 3 minutes apart, Drew conceived first, was born first.

In 1992, Evan and Taylor Barth, conceived 4 weeks apart, were born in Hawaii, USA to Michelle and John Barth. Taylor, the one conceived later was born first. Evan, conceived first, was born twenty-two minutes later.

fertility drugs like clomid cause a woman to release more than one egg. if she bangs two dudes in the 3 day window each can be fertilized by a different sperm. they are not identical they are fraternal, unless one egg divides and she has triplets or something. It would happen more often but most people who are on fertility drugs are married and have been trying for quite a while and are sick of sex.

I know it's possible for cats and dogs to have litters with more than one father. We're all mammals... so I'm going to go with the above poster and say yes. (Possible but not probable)

It is possible to have "two vaginas".

I've seen it on two tv shows.

Maybe they are not twins. They are two seperate fetus' that are not identical nor fraternal twins.

Impossible

she cant