Wasn't Mamoru originally contracted with Madoka though? This is weird, because just a bit ago, Madoka and Megumi had resolved themselves to keep Mamoru within their ranks; and where the heck has Megu been this past month+? Recently in chapter 17, Mamoru reflects to himself "Let's be honest...Just about any assistant can help Ruriko...But only I can help Madoka." He'd also said that his working with Ruriko was a one-time gig. Did the author just forget what the hell was written two chapters ago? Ruriko is already treating Madoka like a pest, so she can just fuck right off, lol.
Another thing to consider, is why in the ever loving fucking Christ did Madoka and Mamoru agree to continue working next door to Ruriko, when there is a door between work spaces, a door that just anyone can open, at anytime. Did neither one of them think "Hmm, what if Ruriko (or anyone from her office) comes in here while Madoka is diddling herself for 'work'"? Madoka obviously has wanted to keep that a secret, and up until now, only the few people she directly worked with knew about it. Regardless of what Ruriko says, Madoka is now in a very compromised position, professionally. All this stupidity is just an artificial means of creating drama and tension.