Do I leave a tip for a haircut even though I may not be 100% happy?

I just got a haircut by a new hairdresser. I chose her because of the good job she does on the girl I know and getting a great recommendation from her AND seeing her for a consultation first. Well, my cut didn't turn out exactly like I thought it would be according to the picture I showed her or the explanation she gave me beforehand. Trust me, I even had her go over everything twice (once at the consultation 1 week ago & again today before the haircut). After she was done and noticed the things I was uneasy about I told her about them but she didn't "get it" (i.e she gave me her reasons for cutting the short side of the side bangs too short, cutting the back layers too short, etc) - maybe it was because I was saying these things but still using a nice tone of voice- I dunno. Anyway, I felt that it was right to at least leave a 15% tip even though I had all these feelings about the cut because she was nice enough to honor the coupon I lost and she was patient with me even though I was nervous and so inquisitive before she started. Yes, this is something we should expect in customer service but it's not what we get nowadays. I know it's too late- it's not like I can get my tip back. But I'd like to get unbiased opinions from people and I'd like to get an idea of what I should do next time. Thanks, in advance.