Clarification

Do you have to be in DDI to accumulate points?

As long as you and your soulmate are nearby, you'll gain points anywhere.

You can get romance points while resting at a campfire near the torch, while picking silvervine fruit, and while fishing. You can also get romance points being near your soulmate in Erinn.

So basically: Just stay near your Soulmate.

Stay near your soul mate at any location, doesn't matter what you are doing (Dungeon, in avon, theater missions, flying, underground...etc), and you will get points...albeit slow and time consuming. Better off dancing and doing the psychology test.

Doing all three is best. Managed to do it in 5 hours.