It is very important to establish this during contract negotiations. The VC is playing a vital role however it is up to the company to establish how involved they want the VC to be involved. If the VC is on the board they have some say so. If they are simply there in a mentorship capacity it is very important that the company have creative control but within reason maybe the VC saw that same vison fail and they can offer some insight on a different approach. Stating that decisions are being undermined carries such a negative connotation it needs to stay out of business. This is a trust issue in business you need to be able to iron out different' s or you have to find other partners, investors, VC's etc.
We all see that building strong relationships is vital to the survival of a company you can only stand united. If the leaders are not in agreement what does that say about a collaboration of the company itself? Make sure you are in agreement once you leave a meeting. If you feel it did not go your way maybe address the issue in a non combative way to make sure you have the right fit so you can keep moving forward. Often it is simply a misunderstanding of intent get it crystal clear so the word undermine does not have to be felt or ever said within your company.