Will she be rewarded for reciting the remembrances (adhkar) that she pledged to Allah to recite, even though she sometimes forgets to recite them?

You will be rewarded for reciting the remembrances (adhkar) you vowed. The obligation of fulfilling the vow does not prevent the attainment of reward, for Allah praised His righteous servants (al-abrar) for fulfilling their vows, saying: "They fulfill [their] vows and fear a Day whose evil will be widespread." This includes what Allah has made obligatory upon them and what they have made obligatory upon themselves through a vow. Fulfilling the vow indicates their eagerness to perform the original obligatory duties.