Absolutely not! As we grow older, it takes more stimulation for us to arouse and lubricate, and that stimulation can come in many forms--physical or mental.If watching an erotic video provided visual stimulation for you... well, you're not alone!
It's sometimes a challenge to find the right material--arousing but not offensive--but it sounds like you found it! Don't feel guilty or embarrassed. Most women need to change things up a bit and adding erotica is a perfectly acceptable option.