maemo ? well there is tabletDJ (mixx) but I think it didn't and wont get any where in developing
https://garage.maemo.org/projects/tabletdj/

and seriously your wife won't be able to do much PRO work through tablet even if it was ported as is (many options to be fitted within 800x480) and separating all these options into many windows won't give be a pleasure for the end user.

Also, check this out (15 programs)
http://www.linux-sound.org/ddj.html with exception to UltraMixer which you will need to buy & get it working through java (easydebian?) add to that (kaffe? or GNU Compiler for the Java? and similar)

Anyway like I stated before, I think the only problem is on the GUI part.

Bounty would help (The higher the better).