My wife is traveling to Myrtle Beach to visit her in-laws Jul 12 - 20th or thereabouts. I found a good price for me to come down if I leave earlier in the month. The airline charges $100+ to change her ticket out for an earlier flight, but if just do a round-trip ticket for her the opposite direction (and just skip the first flight entirely) it's much cheaper.

Can I book a round trip ticket and just use one leg of it? I read the carrier contract and I couldn't see anything explicitly denying it. Only that you couldn't miss a segment, but I assume that means for connecting flights one one of the directions you are traveling, not there - and - back.