I'm not her sister's lawyer or something, but she is kinda normal and is not known for that kind of episodes. Dunno which problems you're talking about.
And she's way hotter than Wanda.
Sure is hotter and definitely more of a girl next door type.
The issues at Atlético were as much her doing as Diego's really. Basically, fans noticed that whenever she came visit a whole circus act of paparazzi, tabloid-style reporters, interviewers, etc came along... and that it affected his focus and performances.
Here in Uruguay we were concerned as well going into the 2010 WC, but we know how that turned out... The problem ultimately was the Atletico fans perceived that dip and its link to her visits, were vocal about it, and Diego pretty much made it clear they could go do one. The bridges were burnt.
I also know from good sources that when he canceled their wedding the whole thing boiled down to him realising he didn't want to marry her family (gold-digging parents, in particular).
So yes, you are right there's nothing specifically wrong with her sister. But the dodgy entourage and thirst for media attention runs in the family.