Was I rude interrupting someone stuttering when I knew the word they were trying to say?

Was I rude interrupting someone stuttering when I knew the word they were trying to say? Hi there. I don’t stutter but I did encounter a situation with someone that did awhile back and I’m just curious on people’s opinions on how I handled the situation. I was walking downtown with my family and dog and we decided to stop at thrift store. I sat outside because I didn’t think dogs were allowed in but an employee welcomed me and him in. Anyway, I walked up to a clothing rack and as I was sorting through it another employee walked up to me. She leaned over, put her hands on her knees and started to ask me “Can I p-p-p”. I’ve been friends with someone before who would stutter on m’s but I never ever interrupted him. Anyway, I could see her visibly start to get frustrated and it was very obvious that the word she was stuck on was ‘pet’. I smiled and interrupted her by asking “Would you like to pet him?”. Now, in my eyes she breathed a huge sigh of relief, looked up and said yes please. To which I of course said yes because my dog loves attention. My question here was even though she seemed relieved and it was obvious what she trying to ask, was I out of line? Should I have waited for her to say the word herself?