Number of times died: 16+10 times.
1 in Doctor Strange #12 (Implicit)
1 in Marvel Two-In-One #7. (Implicit)
1 in UXM #107. (Implicit)
1 in UXM #108. (Implicit)
1 in UXM #113 (in the opinion of most of her fellow X-Men for the next 12 issues)
1 in UXM #137 (As everyone believed at the time, and for the next five years)
5 in Avengers #314 (Implicit)
1 in Infinity Gauntlet #2
1 in UXM #281
1 in Mys-Tech Wars #3
1 in The Adventures of Cyclops and Phoenix #1 (soul separated from her own body for a solid twelve years, from her point of view!)
1 just before the start of Captain Marvel #6 (fourth series) (Implicit)
1 in New X-Men #148
1 in New X-Men #150
8 times (at least!) in Phoenix: Endsong #3.