Depending on version either 'bookmarks>organize bookmarks then select export as html and send it to your docs folder if it's V8 or later it's 'bookmarks>show all bookmarks then as above. Importing them is similar.
However since you cant open FF then you need to look in C
users>name>app data>mozilla...next bit depends on operating system but you should be able to find the bookmarks backup folder and copy it to the docs folder.
As for not starting does she leave the M/C on all the time and just puts it to sleep or hibernates it over night? If so shut the m/c down, switch it of at the mains, leave it for a few minutes and then re-start it
look at
Firefox will not start | Troubleshooting | Firefox Help
which may give you the answer you need.