I would think
1 - Problems w/ phone (disconnected, lost & cannot afford replacement, stalker issues, etc.). I just went a month without my phone, because I had to choose which bills to pay (court stuff is VERY expensive)... And beyond that have major problems with my ex. Since either all or most of your contact attempts were via phone, that could be an easy "Aha" kind of thing. Also, since her VM is full (and most services allow several hundred messages) this would seem to substantiate this theory.
2 - Her divorce could be uglier than she's been letting on. All y'all on HERE know how vicious and nasty my divorce has been, but I do NOT share that with most people. Maybe 2 people know the whole sordid mess, and 5 know "most". This is 2 on my list, for obvious bias.
3 - Crisis. Sick relative (mom in hospital, sister diagnosed w cancer, best friend hit by car.). Son is sick (at a childrens hospital). Etc. Realized for WHATEVERA reason that she needs to stay where she's at and paying rent is silly because she'll be there for months. Had someone pack her out (or did it herself).
4 - Evicted. Money problems.
5 - Ran. Divorce/Custody problems.
6 - Happy. Best friend / mom/ etc. invited them on long vacation.
7 - Happy. Got accepted into a school program on short notice. (Culinary, police, etc.) so her son is staying with family while she's in live-away school
The list goes on and on. There's just so many reasons it COULD be. You may even have made the "Tell" list, but on short notice, you weren't home / text lost to ether/ note u def the bushes in your garden/ etc.