Maybe, but as for me, i think Yuzumori rly has that feelings. Yes she is still kid, but in a same time she is much more mature (compare to Mimika) and the way how she acts (this jealousy and a wish to monopolize Mimika). Its more than "like".
PS: its only my view.
Nah. As sad as it might seem, Yuzumori is a very lonely girl with few to no friends and, presumably, child of a single mother. Of course, she wouldn't want to lose her best friend to some other random girl. You even see that kind of "jealousy" between groups of girls, but it doesn't mean they're lesbians.
As far as the series goes, there is nothing that hints that Yuzu actually likes Mimika romantically.