If the sizes fall in between, choose the most comfortable size up or down, according to personal preference. Usually for rings with big ornaments, choose the lower size for a snug fit, but loose enough to slide over your knuckle.
The most accurate way to measure the Ring Size is to get the ring finger measured in Jewellery stores and take down the sizing in MM. As the Jewellery stores might not be sure about the type of sizing metrics (eg. USA or Japan) used, it will be best to measure in MM and use the Ring Size Chart in this page to find the correct Love Divine Collections sizing.