I never even heard anyone say that before in my life but could just be the type of people I hang out with are reasonably respectful to others and to women. I do not think it is that bad though, disrespectful but there is worse things out there that could be said.
I don't consider "she got practice" dirty sexual slang at all. I didn't even think it to be sexual until I finished reading the sentence. It isn't overtly sexual in meaning, and even knowing how it is intended, it is somewhat chaste in comparison to other phrases that could be used.
But it does sound like something a 14 year old virgin would say because he thinks it is dirty. If I heard that coming out of the mouth of an adult, I would have to seriously appraise their maturity and education levels. Not to mention that the phrase just give me a grammatical migraine.