[Note: in the exercise, "maybe"—which is fine—was given as "probably," which is incorrect, and is the sentence I'm commenting on.] Since this is the indicative mood of होना, "शायद" inserts doubt, so should be translated as "maybe" or "perhaps." If होना were in the presumptive mood—शायद नेहा सो रही होगी—then "probably" would be an acceptable translation.
Probably yes. The meaning and mood are the same in both expressions. But, I don’t think that insisting on the accuracy of translations in different variants, may help us to learn Hindi. It may be useful that in the higher levels of this course we have more translations from English into Hindi or better still from Hindi to Hindi in the form of Q&A.