Similarities with The Undying - SPOILERS, don't read unless seen both

- Grieving woman (husband dies in vehicular accident) rents house in small town
- Finds photo of man who died in house, relationship with his ghost trapped there
- Old handwriting fills in details (very common in ghost movies of course)
- Ghost takes solid form (from very different mechanisms)
- Concerned female friend tries to get women to socialize
- Woman throws away prescribed psychiatric medication
- Obsessed, unwanted person who barges in gets killed by ghost
- Ghost becomes dangerous to woman
- Police, alerted by third party, show up right after confrontation
- Last scene: owner walking away from house

There are big differences, of course. In Undying ghost is benign - malign part is original body/spirit, more of paranormal romance than a supernatural horror that is an inversion/critique of paranormal romance, woman never really falls in love with ghost but is more a codependent friend and then learns to move on. Undying also has a more convoluted plot, and the ghost inhabiting a comatose body is a very different take.

I think all of these are coincidences; Gothic-style ghosts tend to be in old, isolated houses, grieving person contacting ghosts is not new. Such coincidentally similar movies are quite common, largely the result of so many movies being made - more than ever in the digital era.