
Hi Kizzy
I have recently had exactly the same problem, introducing a male GSD pup to my nearly 3 year old bitch. He is now nearly 7 months old, and he is not a constant pain with her now (not to say he isn't a pain some of the time).
I intervened when I could see she had had enough, and I taught him the word 'away' which meant he was to leave her alone. Because he's such a foodie, this wasn't hard to do, and when I say away now, he immediately arrives in front of me for a treat. Of course he goes straight back to her afterwards, so we have a lot of awaying going on, but he is learning well, and also maturing so he doesn't feel such a continuous need to be jumping on her.
They spend quality time apart, when my girl is off with my husband doing agility, he's at training class, and we also walk them separately on occasions to ensure his confidence without her around, and to give her special time. She also comes up for a nap on the bed with me some afternoons, and he stays downstairs.
Also, if you have other adults in the household, I found that my husband and I could run mini training sessions with them at the same time, helping to get their focus on us, and less on each other, only little fun sessions, but it all helps. The one thing I personally would not do, would be to continually separate them, as I feel that this heightens the excitement level of the pup whenever he sees the other one, so he will be continually stimulated to be excited when he sees her. Just a personal feeling. It is better if you gain control of the games and he learnes to leave her and settle in the same room as you and Kizzy, gradually then there will be natural play times and chill times, which if they are anything like mine they will enjoy hugely. I know that they are all different, but this was my approach and it has worked very well. They both know that if I say 'that's enough' they both stop (sometimes she's as bad as he is) and relax.
My bitch also doesn't really tell my boy off as often as I would like, but has done more since he has grown, and I do think that you should, as others have said, let her be 'alone' with him, out of your watchful eye, and she may take more control.
I felt it imperative to gain control, as already at less than 7 months he is two inches taller than she is - BUT - she is still the boss, and I have reinforced that in all ways.
Don't worry, I'm sure it will work out, and they will have great fun together.
Kat