Tipping for cat sitting

Hi everyone. I’m pretty new to Rover & have a question about tipping. I was recently out of town for a little over a week & had a very nice lady drop in on my 2 cats. She seemed to do a fine job & sent plenty of pictures while we were away. There were a few things that I was a little disappointed about (their water fountain was out of water when we returned so that was never topped off & she texted me a lot of questions that were all answered in the note that was left on the counter). Is a tip expected for drop in visits? If so, how much? I was going to tip her but wanted to make sure I was tipping correctly. Thanks!