[watwut]

Exactly. Mature adults form relationships with other adults. There is nothing wrong or icky about it. The more time people spend at work, the more likely they are to find partner there. Note that startups often not only expect long hours of work, they also expect you to spend a lot of time socializing with colleagues.

Expecting her to reject potential stable long term relationship just because the guy has the same employer does not sound reasonable to me. Plus, we do not even know whether they started to be together before she joined the company.