Auto Insurance Claims: Rental Car Liability, collision damage waiver, rental car company

Question
I'm about to rent a car with my sister-in-law to drive to a family funeral which will require a 5 day rental.  I will be putting the rental on my credit card and she will also be a driver.  I don't own a vehicle so I don't have an existing policy that would cover liability - my sister in law does.  My credit card covers damage to the rental car so we won't need to take the extra damage waiver.  Would my sister-in-law's policy cover the liability either for her when she's driving or for both of us if she's a listed driver on the rental agreement? Or will the fact that it's my credit card negate using her policy altogether?  I'm asking her to find her policy so I an read the relevant section(s) but I thought there might be a standard answer to the question. I hesitate to ask the rental car people because in my experience they're not all that well versed in minutiae and the default reply to buy their waiver for an extra $50 over five days is in their interest.  If you can shed any light on this or on what specific wording to look for or questions to ask I would appreciate it.  Thank you.

Answer
HI Joe,

This is a difficult situation, but I will do my best.

Generally,  the rental contract, the credit card used and the primary driver all have to be the same person. So I really do not know what to tell you other than you will need to buy both the the collision damage waiver as well as liability insurance from the rental car company.

I hope this helps
Richard Hixenbaugh