Business Parner and Sister trying to blame me for her possibly getting fired by a client?

Ive worked a long time managing clients for large projects. Ive been in Sales, Ive been in Marketing..worked for 4 top fortune 100 companies..Most recently a top 5 tech company. I left because the hours were horrendous and my sister was encouraging me to start my own business. So I did... She didn't have a lot of bandwidth for a new client.. So she gave me the bottom of the barrel tasks.. which I gladly accepted.. Well here we are 6 months later...Ive now started taking on all of these crazy tasks like PR, Graphic Design, Email Marketing.. Which I all have experience in...Again all because my sister didn't have "time".. The client is super please with these services.. But recently expressed dissatisfaction with my business partner/sisters services (social media) in that they were way too expensive 15k a month... and not effective.. which to a degree one could argue..I told my sister in hopes that she would lower her price in order to keep the client. I told her the clients concerns to give her a heads up, as the contract IS nearing an end.. And I thought if my sister just made a few adjustments she could keep the business. Well it totally backfired, and now my sister is blaming me.. Saying all these things like "I have way more experience than you, the only reason she likes you is because you are cheaper (which I am at 6k per a month), I feel like this is your fault, I don't appreciate how you don't find value in what I do (which isn't true, and I have never said, but the client has)… My sister believes the client is going to fire her.. and hire someone else for social media.. which I guess some how she believes is all my fault. Im at such a loss.. Trying to understand how this IS my fault..shes so mad at me and all ive tried to do is help her. How do I get her to see its not my fault? That just because I advised her to lower her prices based on a.) her competition and B.) BECAUSE the client has complained that she is too expensive for social media services.. that this is not my fault? I have nothing to do with social media, or what the client thinks. I was just the messenger.. She cant seem to get past it and is so mad at me.. Saying we wont be doing business together in the future. What do I do to not make my sister so mad at me?