Let her too wake up to a hot coffee.
(or)
Let her wake up to a hot cup of coffee too.
Here I am trying to convey that what she does for you everyday, you do it for her too. I want to use the first sentence because the usage of 'too'after subject emphasizes more on the latter but I don't know whether it is grammatically correct.
Both of your sentences are grammatical. However, most style guides would recommend putting the too in your first sentence between a pair of commas.
For instance, The Chicago Manual of Style (17th ed.), 6.52:
When too comes in the middle of the sentence or clause, however, a comma aids comprehension.
She, too, decided against the early showing.
Following that guideline, your sentence would look like this:
Let her, too, wake up to a hot coffee.
But that's a matter of style. It's still grammatical without the commas.
