Most Helpful Girl
Just be friendly but superficial with her. Ignoring her shows you haven't moved on.
It's difficult when you work with her, because you're bound to feel awkward around her , but you don't want to cause an uncomfortable working environment for yourself. So speak if you have to, but don't go out of your way to initiate contact
Most Helpful Guy
However works best for your emotions, don't fake it. If you it's best to avoid her and talk to her when necessary then I would do that. After awhile you will find it less awkward and be able to talk. One of the reason why it's risky dating someone at your job.