Sarah you are very rude

So I was waiting in a line, Sarah had put up a closed sign due to a customer exchanging an item or something to that effect, I noticed she was done with the customer so seeing as the line I was in was busy, I asked if she was still closed or if she can help me. Sarah thinking I only had one item or something said she can help and what did I want. I told her I had my trolley and if she was closed or was she opening to which she rudely replies she's closed. She then starts chatting with another staff member for about 5 minutes at which point I moved to the front of the line I was in, clearly she was not bothering about assisting me cash up as she conveniently opened up her till at this point which irked me to say the least, if you have time to have chats with other staff members surely you have time to help customers who to say the least helps your company and helps you keep a job.