Well I guess some obvious things could be mentioned to start.

Summer in north, winter in south. In some places in the south, though, winter = dry, so some safari areas in southern Africa are best around then. Dallas pretty well defines summer heat, so aside from hot/wet places or the Middle East, climate may or may not be a consideration.

Probably best to load the OW timetable and go down the list of cities to see what hits her fancy. Easter Island? Skiing in New Zealand? Midnight sun in Scandinavia? Great Barrier Reef? Scottish Highlands? Barcelona? Victoria Falls? Hong Kong? Yikes... where to start.

Have her browse some of the trip reports on that forum, or visit some of the other travel websites like fodors.com - so she can start narrowing down the humongous list of possibilities that are out there.

Ediited to add - I can't believe I kept using "she" and "her" - as if I was replying to Blumie instead of you, kristyek. Very, very sorry.