A girl asked me for my number. AITAH for what I did next?

A few days ago I was studying at a cafe in my college town when a girl approached me and said I was cute and she asked for my number. I was flattered by her approaching me, but I did not find her attractive unfortunately. However, I got nervous because that rarely happens to me so I just gave her my number anyway.

A few hours later, she texted me saying "Hey it's [name] from the cafe!" At this point I didn't know how to handle the situation and whether or not I should respond -- I was not interested in pursuing her romantically or even becoming friends with her. So I asked a few of my friends for advice:

The first two friends I asked told me the best thing I can do is either reply to her message and tell her that I'm not interested right off the bat, or just not respond at all. The other two friends I asked told me I should respond to her and be friendly / get into a brief convo then ease into a rejection message, and the message should be a "white lie" to soften the blow and make it seem like she couldn't have dated me anyway.

At first I was thinking of sending no reply, but then I felt like it would've made her feel bad/rejected so I went about the best way to hurt her feelings the least possible. What I ended up doing was listen to the latter two friends, and I responded to her saying "Hi it's [my name]!" and then she asked how I was doing and I responded to that and then she asked if I was free to call her sometime later. In response, I told her I was busy, then I told her "Also I didn't know if I was gonna be the one to tell you this, but I'm gay lol" which is not true and just a white lie to make it sound less like a rejection. Also, this whole text exchange lasted only 20 minutes.

After doing this, the first two friends I asked for advice told me that what I did was not morally right and that I should have been honest from the start. Their view is that it's more respectful to be transparent even if it stings a bit. My stance is that I was trying to be empathetic and protect her feelings, and that it wasn't serious enough to require complete honesty since we didn't know each other.

I feel deep down that what I did was right, even if it may have been unconventional. But now I'm wondering if lying about something like that makes me an asshole.

AITAH, or was it understandable in this situation?