For my sim, she had disciplined, athletic and brave traits. Also her athletic skill and martial art skill were all 10. I thought she would defeat mummy very easy but I guessed totally wrong. She lost against mummy and even the mummy cursed her. It would be the best if she was in that quest but actually she got cursed in Isael's tomb of France. OMG.. After she completed all nectar quest under nectary, she straight to go to Sphinx in Egypt. It happened just a month ago.
Sometimes, it's possible to get cursed by mummy although your sim is very brave, athletic and its skills are maxed out. I just saved my game before fighting. If your sim defeats it, just go back to the main menu, and try it newly. I've done that process 5 to 6 times, eventually, the mummy cursed my sim. It happened 2 years ago.
