Maapa: maap "who" with -a question suffix. The question suffix is not usually seen on the question word in a sentence like this, but usually goes after the verb.
Memeyaap: "You are with", appears to be the second-person form of maayaap (more often maayaayp or aayaayp, but also aayaap in Mesa Grande) "is together with (someone)".
meyu: Question particle used for second-person questions. Usually preceded by -ch same-subject suffix, omitted here.