As someone who's also been an early employee, I totally see why Heather does NOT claim to be a co-founder. When you work your ass off alongside the founders, you learn two things:
1. Building a company is incredibly hard.
2. Nobody takes it harder than the founders.
Yes, I have worked hard. In the last six years, I always worked parts of my weekend if not my vacations (which were few and far in between early on). I pulled off all nighters as well as a last minute trip straight from work to close a customer. I fell asleep on my laptop answering support questions. There were many nights of dry tears and waking up in cold sweat from nightmares that were all too real.
But what I went through is a fraction of what the real founders went through. And I saw their ups and downs up close.
Startups are hard. Incredibly hard, especially for those who has to lead the ship from Day One. Early, dedicated employees see this first hand, thinking to themselves, "Man, I thought I had a good/bad day, but they are probably having it better/worse". That's why we never claim to be the "founders".