Elemental Prince by Megan Fall

Emmalyn Kensleigh is a quiet girl. She lives in a modest apartment with her uncle and works at a local animal shelter. One night, a portal opens in their living room and several large men brandishing swords step out. It only takes a minute to discover her whole life has been a lie.
Now she’s being whisked back through the portal by the sexy, and towering, Kell Hawthorne. The man is a prince in an alternate realm, and he claims Emmalyn is the missing princess, lost to his world twenty years earlier. His world is in turmoil, and he is a mighty warrior able to wield the earth elements. But his power isn’t complete, and for it to be, she must become his bride.
Emmalyn is struggling to survive in an unknown world, dealing with a hot alpha that doesn’t understand the world no, and coming to realize that she’ll never see her home world again. Most girls would break down in the face of such intense circumstances, but Emmalyn isn’t most girls. She’s determined to show Kell that not only can she triumph, but she can do it standing at his side.