Wicked or Hair . Both my favorites and i ve seen almost all of them.She ll love Mamma Mia too.
Doubt you ll be able to get tickets to Lion King - seems I heard it s sold out for months. That s probably the case with any of the major, popular shows, too. If you do a search for Broadway tickets you should get some leads for sites that might tell you what s available. Or, try the TKTS site. You have to stand in line to get tickets through them [either in Time Square or downtown] for the day of the show. One person keeps the place in line while the other goes to the board to see what s available. Tickets are about 50% off. The website has a list of recent availability, which doesn t necessarily mean they same shows will be available the day you re there.