For me, if I like the guy back, there's no such thing as too many texts. Even if I don't like him back, multiple texts before I respond doesn't really even bother me in the slightest. Seriously, it's just a little thing that pops up on your phone, who cares? The only time it does bother me is when a guy keeps asking me to do something I don't want to do again and again, as though he cannot take a hint. That's when I start to ignore.
That's difficult to say. But for me. If I like the guy, I will text him all the time as well. Or at the least answer him. If I am not so much interested I might answer less or not initiate the conversations and only answer. But remember to give her space as well. Maybe not be available all the time, even though you might be.