Welcome to the forum! Most Dobermans play pretty rough. They are noisy and they wrestle and play bite. If you haven't seen that style of play it can seem like it's dangerous, but you'd never mistake it for a fight if you've seen a real fight.
Adolescents, in particular, can be over-the-top in their play. Stuff they got away with as a young puppy might be off-putting to other dogs now. As long as both dogs are having fun, I would not be worried. I would, however, teach them "take it easy" and to take breaks during play, to prevent them from becoming over aroused. Sometimes that means interrupting play and holding onto them separately until they relax a little, then letting them go back to it.
Below is a video of my Shanoa and Simon (who passed in November). This is actually pretty low-key play for the two of them. It's kind of dark, but you can see the biting and hear the vocalizations. This is normal play. There is one split second in the video where it almost turns into a real fight - see if you can spot it. Simon had bone cancer, and I think Shanoa hit him a little too hard at one point and it hurt, so he told her to back off.
Here's the video:
If you aren't super familiar with reading dog body language, it would be really helpful for you to pick up a copy of Turid Rugaas's book, "Calming Signals: On Talking Terms with Dogs." It's cheap, about $10 on Amazon.com, and really should be required reading for all dog owners - it's that good.
As an owner of both Bella (female Doberman, 6 months old, 52 lbs) and Sparky (male Bichon Frise, 21 lbs) I have to TOTALLY AGREE with you!! They fight HARD, but if I watch Bella really intently, I can see its just play! Even with all of the vocalization, growling, snarling and teeth showing and biting, it's just play - HOWEVER, again Meadowcat is right - it CAN turn ugly, especially when the Bichon gets a little too "over the top"! Then i have to separate them or surprise them into changing their mind set (a spray of the water bottle brings Sparky right back to reality and out of the red zone).
One night a few months ago, they were playing very, very rough, and Bella was rolling him in the mud, snarling, grabbing the skin on his back and shaking him with her jaws -- then I saw blood all over Sparky! I sprang over to him in a panic, to check the "wounds"... Strange, the blood was on the tips of the hair, and NOT by the skin... Dear God! After nearly having a heart attack, I realized that Bella had a loose tooth and left Sparky full of HER blood, lol! There was NOTHING wrong with Sparky at all, and minutes later, they were laying under the kitchen table and Sparky was licking her ears, LOL!!
Being able to distinguish play and aggression is definitely a MUST. Getting more familiar with body language is probably the first thing you can do, though, so you can gain more trust in her. I have worked with dogs my entire life, and i have to admit i was a little worried in the beginning too, especially because of their size difference. However, over time I've learned not to worry, that they ARE playing and I also know that if I get anxious, what starts as play can turn for the bad... Your anxiety can change the whole dynamic! So stay calm! You'll KNOW when its a fight - Only the Dobie would be walking away...
I just bought the book "On Talking Terms..." Meadowcat mentioned, by the way. Not because of their play, but because unlocking the mysteries of their subtle body gestures is so utterly fascinating! I was watching them yawn last night when i got home from work and was wondering if they were trying to calm me down, or if they both had just woken up when I got home, lol! Can't wait to read it!!
I'm sure everything will be fine. Relax, educate yourself and enjoy that Dobie-girl!! Stop thinking of her as your husbands choice and truly bond with her, and you'll see an amazing world of difference in her behavior. Good luck!!
And now... More pictures please!! Sent from my iPhone using Petguide.com Free App