Well, do you respond when she jumps on the door? Boxer logic isn't going to take into account that it's annoying or gets dirt on the door - but if it gets your attention and the door to open, then of course the dog will continue.
If you want your dog to stop that behaviour, then you must *never* give the dog what it wants when it jumps on the door. If the dog has *ever* been successful, then it already knows that jumping on the door brings the desired result and - since you have effectively taught the dog that when it wants in or out, to jump on the door - you can expect to have to spend a long time trying to extinguish the behaviour.
The way to stop it is to never (not even once) respond by opening the door for the dog. If you're right there when the dog jumps on the door, then by all means tell it 'no' and redirect to some other activity (a toy, for example, that does not involve opening the door). Do NOT open the door any time soon. If you're not right there - then you have to absolutely ignore the behaviour. As long as your dog thinks that there is a chance that you will respond, give attention, or open the door when she jumps on it then she isn't going to stop. Why would she?
As with any training for a dog - the key to success is absolute consistency and patience on your part
Reward (with attention, praise, or whatever the dog wanted) ONLY the behaviour you want to encourage. If you reward behaviours you don't like, there's no point in complaining about the behaviour afterward - because you taught it
As a last thought though - if your pup is jumping on the door to tell you when she needs to go outside, and you don't want her to use that method to let you know, then you really should be giving some thought to teaching her an alternative method of letting you know when she needs out.
