The problem is not that you are a feminist, it is that you were text messaging instead of talking on the phone. It's very hard to communicate nuance, levity, and emotion in email or text messaging. More importantly, it's very easy to infer signals through email and/or messaging that were not necessarily intended. And emoticons are really no help here at all. I bet your grandma prefers talking on the phone, and in this case, she's right.
The problem is not that you are a feminist, it is that you were text messaging instead of talking on the phone. It's very hard to communicate nuance, levity, and emotion in email or text messaging. More importantly, it's very easy to infer signals through email and/or messaging that were not necessarily intended. And emoticons are really no help here at all. I bet your grandma prefers talking on the phone, and in this case, she's right.