Like JesseKomm said, she is definitely a smaller merc (like Sparks or Proxy, which also have this sort of issue), although I don’t believe they actually sit much lower than other mercs. Of course a Fragger on an MG turret is going to be much easier to hit.
And also, the hit-boxes for the actual MG’s are very hit-and-miss at the moment, they need to be fixed big time, not only for collision but trajectory impact too - I’ve tried shooting people on them before, only to notice sparks flying off thin-air where the bullets are hitting the “turret”.
I imagine this will be worked on in the future, as I don’t see it as a high priority now, but I certainly mostly agree. Might I suggest, if you take a screenshot of it or something, posting about it in the bug reporting section, as it could definitely be not intended. All the reports in that section are looked over commonly by the QA team for testing. 