for or with

[Unregistered]

She is working for Microsoft company in SAn Francisco

or

she is working with Microsoft company

 

[emsr2d2]

She is working for Microsoft company in SAn Francisco

or

she is working with Microsoft company

If someone is actually employed by a company, we normally use "for". If someone is freelance but is doing some work at the request of that company, we would use "with".

Note that you don't need to use the word "company":

She is working for Microsoft in SF.
She is working with Microsoft.