It is possible to translate "בודד" as "single"?
No, בודד can mean "single" as in "just one", for example: אכלתי תפוח בודד (I ate a single apple). It doesn't mean "single" as in not dating anyone (that would probably be translated as "פנוי"), so it doesn't fit here.
Constructive question, though! Thanks :)
The proper translation would be "since she left him he has been lonely."
מאז שהוא עזב אותה היא בודדה.
Aren't there loads more guys waiting in line to get with her though?