This is a tricky way of asking what is she going to drink. Because of potential confusion in speaking "ce va" and "ceva" sound exactly the same, the Romanians are either saying: - Ce bea mama ta (if this is about people sitting at the table and having a drink) - Ce o sa bea mama ta (if this is about planning something in the near future)
Doesn't "Ce va bea mama ta?" stress the question marker "Ce" in spoken Romanian? I've never heard a confusion between "ceva" and "Ce va" in speech, especially since by stressing the "Ce / What", you're setting yourself up to voice the following future tense ("Va +verb, "bea" in this case) together in one breath, further eliminating the confusion... Also, if using "Ceva", then the sentence order would be taking a poetic license, as it more naturally flows as "Mama ta bea ceva(. / ? / !)".
TL/DR: Not sure there's a confusion to be made but maybe I'm wrong here...