Sister is rude to my GF?
My sister( age 20) is constantly making fun or being rude to my girlfriend( age 18 as am I). A little backstory though. I'll be honest, I met her when a buddy of mine and I went to Hooters haha. She was cool and I tried a few cliche pick up lines( I made a joke out of by having her watch me Google "Pick up lines" on my phone and asked her to pick her favorite one). We had fun and I asked for her number and she wrote it on the check with a 
next to it. ( needless to say she got a nice tip. $20). So we texted and went on a few dates and now we're 3 months in and in love. Anyway, my sister is in our business. We'll be on the couch together and she'll come in and say stuff like " ( my name) I thought you'd have a hickey by now * looks at her* good girl". A few days ago, we were outside tanning and she had her bikini on and my sister came out and told my girl to " respect our neighbors and put some clothes on". The one thing that really pissed me off was when she flat out said " You know he only likes you for your looks". I've talked to her but she won't stop.
she's dating a guy for 5 yrs now
Comments
I think you should show your sister her place and protect your girlfriend. Every time your sister is rude, you just make sure that you don't let it go. If she tells your girlfriend to get dressed, you say that you like her in bikini. If she says that you like your girlfriend for her looks, you say that you are capable to tell your girl yourself why you like her, there is no need to assist. If you sister does not respect your girlfriend, she should at least respect your choice. Don't let her ruin your relationship.