Is she considered an unbeliever for not repeating the prayers she performed facing the wrong Qibla, knowing that she has started repeating them now?

If a worshiper exerts their effort in determining the Qibla (definition), their prayer is valid and they are not required to repeat it, even if it later becomes clear that there was a slight or significant deviation. However, if the deviation invalidates the prayer and makes it obligatory to repeat, delaying the repetition is not considered disbelief (kufr). Some scholars hold the view that making up missed prayers (fawait) can be done at leisure, not immediately.