Will she be fluent? No,
probably not.
Will she benefit? Yes, definitely. You can easily look up how language exposure is good for kids and such, but I wont bother to quote that stuff here just now.
Can it work? Absolutely! Bravo to you mama for putting in the time and effort now. I really think that putting in the time early on will reap huge rewards and benefits for your childs language development.
Is It Too Much? No, I don't think so. If its a part of your days routine etc and just a nice activity you all do together, there is no reason not too,
I say you just need to be consistent. Explain to her some vocabulary before each story, point out the vocabulary from books in real life and be regular with your exposure. If you do something like
calendar time with her, just add a short discussion about the days story time language to the routine, just to help her see the boundaries of each language.
("Today is monday, what langauge is our morning story time on monday? German! Good job, today we're going to read our books in German...")
As you get used to the language rotation and her comprehension grows and such, you might start doing a regular craft project, simple things, but during that time you speak language. This will let you speak about colors, shapes, actions (cutting, pasting, coloring, etc) and give sentence structure.
As she grows, you can do more and more advanced things to help her build her speaking, listening, etc
You might set up a special toy basket that calls for role play (plastic food, dress up) and during that time with that specific toy, you speak ____ with her.
Play restaurant in German, speak English when you're cooking together.
I recommend the Opal Dunn book, Help Your Child with a Foreign Language.
I'm really enjoying it