If there is a credit card in her name it is easy to just put money on it, get a bank statement as proof that she has enough credit-card funds for her portion of the traveling. This is what my friends have done.
You cannot choose sponsor as far as I can tell, because a sponsor is a company or person resident within the Schengen area. If you do know a person living in Schengen area then that might be easy way though :)
If she has no credit-card a simple bank account in her name with a bank notice proving she has enough Cash should be sufficient too.
You have not specified from where or to what country you are applying for the visa, which will change some of the rules. A bank statement of 450 SEK per day is what the Swedish Migration office asks for.
Sweden requires that you have SEK 450 for each day spent ...
You must be able to demonstrate that you have sufficient funds for your keep with the help, for example, of bank statements ...
From the Swedish Migration Office website.
To be on the safe side I would ask the appropriate embassy or embassies what kind of proof is required and then check the equivalent section of the application form.