This expression is an NP-ADV, and the NP-ADV is placed as a sister of the whole coordination structure which follows it; it is attached high and immediately dominated by the phrase which dominates the coordination structure. This is nearly the same as the position of "both" or "neither" in correlative conjunctions. See HVORUGUR and the documentation in the English corpora for correlative conjunction.
(PP (P svo-svo) (CP-ADV (C að-að) (IP-SUB (NP-SBJ (PRO-N hún-hún)) (BEDI var-vera) (ADVP-TMP (ADV ávallt-ávallt)) (PP (P í-í) (NP (NP-POS (NPR-G Guðs-guð)) (N-D þjónustu-þjónusta))) (, ,-,) (NP-ADV (OTHER-N annað-annar) (NP-POS (NUM-G tveggja-tveir) (PP-PRN (PP (P á-á) (NP (N-D bæ$-bær) (D-D $num-hinn))) (CONJP (CONJ eða-eða) (IP-SUB (NP-SBJ (PRO-N hún-hún)) (VBDI hugði-hyggja) (PP (P að-að) (NP (NS-D SPÁMANNABÓKUM-SPÁMANNABÓK))))) (CONJP (CONJ eða-eða) (IP-SUB (NP-SBJ *con*) (BEDI var-vera) (PP (P í-í) (NP (Q-D NEKKVERU-NOKKUR) (ADJ-D góðu-góður) (N-D verki-verk))))))))))) (. .-.)))