Look at your growth chart in the red book, baby should be roughly following the same 95th percentile line. Fundal measurements are very inaccurate, I wouldn’t really blame her judgement for that, most midwives and consultants wish they weren’t even part of the process.
Like others have said check your red book and see if she's following the line - it's ok if she gradually increased too but if it was a huge leap up suddenly they'd probably keep an eye on it. They're supposed to put on around an Oz a day at this age
My baby is also a big baby - born 9lb10oz and by 5 weeks was 12lb9oz and I was measuring average through pregnancy too. His growth chart still shows him being around 97th percentile which is what he was at birth so I'm not worried about it