Covens are funny things. You can have one group which is all rainbows and sparkles and unicorns and everyone gets along by doing their own thing, and then right next door there's a group with a twenty-page list of rules and guidelines, where everything is planned down to the slightest detail. Both can work well -- or not. What determines how well they work is not whether there are rules, but how the members of the group choose to respond to those rules (or lack thereof).
Since you're the one forming the group, it's up to you how it's going to be run. It sounds as though your former HPs ran her group in a way that worked best for her -- but that doesn't necessarily mean her way will work for you. Realistically speaking, any time you have a group of people coming together for a common purpose, it's not a bad idea to have at least some sort of guidelines in place for how things will work. Now, you don't necessarily need that twenty-page list of rules. But what you do need is to figure out what items matter the most to you.
Some things you may want to use as a framework for a set of bylaws might be a mission statement explaining what the purpose of the group is, a description of who can be a member and how they are chosen, details on what behavior is expected of members, and what standards of training members are held to. For more detail on how to write a set of guidelines, read Writing Coven Bylaws.