Angela's Material Body is temporaryIt's stated in the movie that DEVA's agents don't like living on Earth and stay in their Material Bodies only as long as their missions require it. Angela also seemed content with merely transmitting her consciousness back to DEVA and only had a problem with leaving her sleeping body with Dingo, which may or may not imply that ditching the Material Body after a mission is something of a standard procedure, especially considering how costly is sending something with mass back to orbit.
Considering all this, there are two possibilities that make the most sense here: One, the material body is kept available for reuse on Earth, probably under cryostasis or another form of long term storage, seemingly in contradiction with the fact that Angela and the other agents sent to deal with Frontier Setter were in a big hurry to build their Material Bodies, suggesting that no one else was available; Or two, a Material Body is meant to be disposable and it's likely designed that way because it'd be a waste of resources otherwise and prevents potential rogue elements, like Angela after the events of the movie, from being a problem for DEVA for too long.
TL;DR: Angela's physical body is preprogrammed to die and a relevant plot element in the sequel Light Novel will be how to prevent this from happening.
- Angela explains as much to Dingo and Frontier Setter before reporting back to DEVA. While the body is disposable, it's destroyed by means of causing total cell death by remote trigger through the DEVA system; backup killswitches were probably seen as pointless since agents would, being as dependent on the network as they were, always be connected. Angela's body has a killswitch, but the detonator cord's been cut.
- Given these AIs are potentially immortal the temporariness of it could be a reasonable human life span (which would mean she was quite fortunate to get one a little aged down).