To put @gailcalled‘s answer in more layman terms. She will lay down, scoot her bottom down to the end of the table, and put her knees up either by putting her feet on something, or they might let her legs rest up. They will likely shine a light on her vagina, which might feel warm. They will use a lubricant like KY and then insert a plastic or metal device that they then open and lock in the open position so her vulva and vagina are in an open position. Relaxing is the best way for it to be not uncomfortable, if she is nervous or tense, pushing down a little can allow the speculum to be inserted more easily. It would be like having a vibrator in there that’s hallow sort of, because they want samples from the back of the vagina, on the cervix. Then they use a large qtip or a long sticklike thingy to take samples from inside her vagina. It will scrape a little, she will feel it, but it won’t be painful, just a little odd. It does not take long at all.
She should tell the doctor it is her first time, so he/she will walk her through the process.