I am worried about my Weimaraner reaching adolescence and what to expect? Will her behaviour change?

I don't think you should worry too much about her changing drastically. I've been around a lot of Weimaraners and I've never had a bad experience. It's always possible for a dog to change, but just be consistent with her, if she's happy now and you keep doing what you're doing there's no reason for her to change. If you get her fixed it might keep her from changing moods. I've never seen a drastic change in a dog just because they reach adolescence. Just don't worry too much and treat her the same with respect and a lot of love.
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All dogs, regardless of breed, turn into nut cases when they reach adolescence. The important thing to remember is that they really do grow out of it. You just have to be patient.

Separation anxiety should not develop from raging hormones. Instead, expect boisterous behavior, inability to focus or concentrate, and general goofiness and klutziness.

Dogs do go through two fear imprint periods. It is a common misconception that these are periods when a dog is fearful. That shouldn't be the case. These are actually periods during which the pup learns how to deal with the strange and unexpected. It is possible for a bad experience during a fear imprint period to damage a dog's confidence, so do you need to be careful. The first imprint period is at about 8 weeks, and the second is in adolescence, around 8 months though it can vary a lot.

If you observe you pup acting spooky (startled, worried, confused), take command. This is when he needs a confident and fearless leader to set him a good example. Do not coddle or comfort him when he is this way. That only tends to encourage him to believe that there really is something to worry about. What he needs to learn from you at this point is how to determine what is dangerous vs what is only weird. So you remain calm. Encourage him to investigate any strangeness that you know will not harm him. Praise any investigation or curiosity. If something really is dangerous, or if he can't calm himself down, take him away from it.

If he does have a strong fear reaction to something that is not dangerous, do not force the issue with him. Instead, do some desensitization work, gradually getting closer and closer to it over the course of days or weeks if necessary. Patricia McConnell has a useful booklet called "The Cautious Canine" which explains the process of desensitization.

You should also be aware that during adolescence many dogs experience "learning plateaus." He may suddenly revert and forget something that he knew really well just the day before, like how to sit, or come. Be patient. That knowledge isn't really gone. If he reverts to a younger age, go back in your training and work with him at what ever level he appears to be, even if you have to go back to puppy basics. The objective isn't really to retrain him to do things, but to encourage him to use his mind in familiar pathways. Keep the brain muscle exercised. Eventually he'll wake up one morning and suddenly remember all the things you taught him and he forgot. It really can be spooky to watch. It can also happen more than once during adolescence.

So the most important thing to remember about adolescence is that your puppy will experience some changes but that he will recover. Sadly adolescence is when most dogs are surrendered to shelters just because owners don't understand it is temporary or aren't patient enough to put up with the goofiness for a few months to a year. After adolescence you have an adult dog. He'll remain more or less the same from one day to the next as an adult and reasonably predictable for the rest of his life. If you help him to keep his confidence and wits during his goofy stage, he'll grow into a wonderful and faithful companion for years and years to come.

Note: she has an added issue in adolescence if she isn't yet spayed. When a female goes into heat she is even more nuts. She is also smelly, messy, often grumpy, and must be protected from making unwanted puppies.
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I would expect as she gets older that she may try to challenge or defy you, its normal. Nearly all dogs try for the alpha (leader) spot at some point. It would be advisable to enroll her in obedience, if you have not - but YOU need to be the trainer, not somebody else - if you want to stay in charge. There is also an excellent book to help you with both fear periods & misbehaviors, "How to Raise a Puppy You Can Live With" by Rutherford & Neil (Alpine publishing). Carol Lea Benjamin also has written some very helpful training books that are also very humorous. Weims are a very bright problem-solving breed, so try to have activities for her & games/toys that require thinking. (like toys you have to work to get treas from.) Weims are very good at tracking & agility. They are also a very active, breed so don't forget the exercise. If you mix up the activities & the types of exercise/play she is less likely to get bored & to demonstrate misbehavior. Write again, if something specific comes up.
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25 yr in Weims, numerous titles on them; in part making sure they had plenty to do, plus it was fun for both of us.

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