A woman travels through parallel universes and discovers different lives, loves and losses. Now she must choose: should she stay in the life she might have had, or return to the one she has?

Nice concept, and you get all of the important information across. You could tighten this up, though – get it all in a single line and not lose anything. It could be as simple as, “A woman, traveling through parallel universes and different lives, must choose between the life she has and the one that might have been.” There are plenty of other ways you could slice it but whichever way you go I think it’s more than possible to keep it to a single line and retain all of your meaning.