Exactly how tall and how heavy? The correct height range for an adult boxer bitch is about 21-23 inches tall, and you'd generally expect them to weigh 50-60lb.
There are probably plenty of bitches who exceed that... but they're oversized (incorrect) for their breed.
As for the weight, what is most important is that it is correct compared to her height. If the bitch is taller than she's supposed to be, for example, then she should weigh correspondingly more (and the opposite if she's smaller than boxers are supposed to be). If you suspect she's too heavy though, then you're more than likely right
Around 80% of pet dogs are overweight - and aside frm doing them no favours, it's also what we beccome accustomed to seeing. LOL - I'd be rich by now if I had a dollar for every obese dog I've seen whose owner claims it's "all muscle"
I haven't seen your dog, of course, so that is only a general observation that may not apply in your case. But it is worth comparing her actual height with the guideine weights you can find in some of the boxer standards from around the world (e.g. the FCI) and figuring whether or not she's generally in correct range. Or just do it visually: you should be able to see the outlne of her last couple of sets of ribs when she's just standing normally. If you can't, she's overweight. If you have to prod to find them, she's fat or worse (and it will ffect her health long term). Soo - take a look, and judge from there whether her weight is good for her individual frame or whether she needs any adjustment