Just like how the sun shines on all beings irregardlessly... so does the Buddha's blessings to all those who help another person in their spiritual growth.
In this case, I would say although her motivation is not set right... but who are we to judge a person? As long as we are not enlightened, anything we do is not from pure motivation. Therefore, what is the difference between us and her? Neither one of us have pure motivation, so why do we get good merits and she don't? She will receive merits from this action... there are many other ways to 'get rid' of statues... the fact that she decides to give it to someone who practices Dharma rather than throwing it into the dumpster is already indicative that even if she does not believe anymore, she still respects the Buddhas.
Of course she could have generated greater merits if she have a better motivation behind it... but definitely she collected good merits. After all, how can one not get any good merits by giving away Buddha images?