You can text her too much but you can't text her too little.
I only have two rules. Never send two messages without a response from her in between, and always be aware of her energy so you can match it.
When she said, "Shopping", you should've just left it alone. She didn't say, "Shopping!!", or "Shopping

". A one word answer like that with no inflection means she's probably busy and catching up with her mom and you're sending texts for the sake of sending texts. Your friends ever send you a "Haha" text and you knew the conversation was over? Same thing. Plus, you don't really care what her and her mom are picking out, do you?
Text her when she texts you, use it to meet up as quickly as you can and wrinkle the outfit her mom just bought her.