So to answer all this:
1. lena has NO boyfriend the guy on hte photo is her best friend
2. SHE hasn't said anything like this just as a joke because in german TV she's asking a lot about him but she doesn't want to say anything about her private live so she jokes about it
3. HE said all this stuff like ''I love her, she's going to win. I would really like to invite her to dinner'' in THIS video himself:
link
and in a german tv show he definitly flirted with her and not otherwise. so no bashing on lena she's really nice.