She's lovely
She looks very much like our Charlie, who also has a longer nose and ears that stick out!
Our Charlie was a rescue and came to us at 13 weeks so we've no idea about her parents, but I suspect the same as Gmac has already explained she's just not been bred by people "who know what they're doing" so to speak.
We go on regular walks with other boxers from the same rescue group we volunteer for, sometimes over 30 boxers and by golly do they come in all shapes and sizes when you see so many together.
She may not looks like other boxers you meet but if she's anything like our Charlie she'll be all boxer in personality and as long as they are healthy & happy that's what matters.