If your partner's visa and work permit are still current, sure she can return to UK and you can accompany her as her partner (do you have relevant visa still current?) As for indefinite leave to remain, I'm afraid she has been away from UK too long to qualify, and has to start afresh (5 years). The limit for absence is 3 months or 6 months in total. Only exceptional compassionate reasons allow absences longer than the limit, such as serious illness of close family member or absences directly arising from employment in UK (e.g. being posted abroad by UK employer). Pity you didn't leave UK after obtaining ILR, which would have allowed absences abroad up to 2 years.