I watched DN again and noticed that the character of Sylvia Trench is either married or engaged.
I had the opportunity to see the film on a big screen last night and noticed this as well.
My suspicion is that it was just a production gaffe and she forgot to take off her ring before filming.
On the other hand, there is a great deal of sexual innuendo in the film, so it's possible that they were trying to hint that the character was attached to someone else.
Also, attractive single women have been known to wear wedding rings to deflect unwanted advances from potential suitors, so who knows?