Ok I am going wayyyyy out on a limb here but do you think Meri's issues with Janelle from the beginning is because although Meri married Kody first, it was Janelle that got pregnant right away and had Logan before Meri had Mariah.
Also as I was looking on wiki, Christine also became pregnant before Meri and Christine had Aspyn before Meri had Mariah. (I believe it was the same year but Aspyn is older than Mariah).
Just pondering a thought as to why Meri had/has issues with Janelle. Deep rooted jealousy. Hmmm.