many teen Girls can be a bit dramatic for attention to start with and then yes she is likely taking it to a further degree based on what she has seen from bm.

Some sisters and brothers can be very impressionable on their siblings and my guess is that the one that went with you had a great time but when she returned home and saw her sister 'sick', she felt guilty and so tried to make it look like while she went swimming, she had an injury to make her 'sick' sister feel better.
My hubby's ex is the same: woe is her and when one of my 3 steps has a sniffle, they all have to stay home from school. When the kids are here with us, they go to school even if they have stomach aches, pains etc. If you throw up, you get to stay home, that's it. My hubby will bring them to school and she will go pick them up when she finds out one doesn't want to go to school.
It is only the kids that will lose out in life, as they do not have the maturity to understand the importance of school and having to go. Clearly neither does their mother but that's their problem then.

Maybe a girl thing? My SD is a hypochondriac, loves the idea of being sick or injured, ever since she was a young child. Her dolls were constantly getting into terrible accidents needing bandages, surgeries, and crutches, it was pretty funny. She lies to her friends about surgeries that happened to her. She has ploys to get us to take her to the doctor when she's "sick". And OMG the eye doctor to check her eyes at least twice a year, (she doesn't know that I know that the school checks her eyes every year, and she has no problems), nor does she know that we know that eyes are unlikely to go out of focus beyond 11 or 12 or so. Her mom is the only one that falls for it and absolutely nothing is ever wrong with her eyes, she just wants glasses-- and she has "fashion" glasses we bought her that she will wear all day long sometimes. If she complains about feeling sick, usually when another family member truly is sick, we usually just tell her if she's not feeling good, she needs to lay down in her room (which she hates to do), so we know if she really isn't feeling good, she's in her room sleeping during the day... which happens about 1/100 times she complains, for as sick as she would like to be, I think she, unfortunately, has been blessed with the hardiest immune system of all of us. A month or two ago, SD went to school with a bandage she created at home around her wrist. Tried to threaten DH that the school would make him take her to the doctor. DH called BS, and told her if it hurts to just go to the school nurse. She never did. DH and I ignored it, and laughed a little behind her back, surprisingly she made it through the whole day without taking it off in embarrassment. Though it came off as soon as she got home, and nothing was said about it again, so she may have gotten teased, but her pride got in the way of actually taking it off in front of the teaser. Who knows. If she was allowed access to social media, she probably would have posted it too.

Raised girls AND boys.

Girls tend to be more dramatic, they just do. BUT if it keeps happening over and over again there might be something behind 'we are what we've lived' which is not gender specific.

Could be her way to seek attention IF that is what BM does. What is her pay off when she does this? 'ohh, nooo...are you ok? What happened, awww you have an Ouchy, can I get you something'......FB is a huge way to get that response.

JMO of course gosh

Girls are more dramatic, but I raised two and they hated being sick. I get with SO and SD was 8 or 9 and was "sick" all the time. Or "allergic" to everything when it suited her. She was highly allergic to milk, but could eat cheese, chocolate, ice cream you name it. The only thing she was "allergic" to was actual milk ***eyroll*** SO was buying special milk (can't remember the name of it) because of her allergy. All school paperwork had to have big bold letter of her allergies and lo and behold when they wouldn't allow her to get chocolate milk at the cafeteria all hell broke loose. So the kid was never allergic to anything she just liked her parents fawning all over her :sick: :sick:

Then she couldn't eat with taking a Gaviscon it's some OTC antacid type of medication. She refused to eat unless she had one of those pills, one day I threw them out and she was beside herself. Well she ended up eating because she was hungry and she was just fine. But to this day she is constantly wanting SO to take her ibuprofen or Midol to school. He never does but she texts him constantly. She is 17 now and she has calmed down a bit about things but she is still a major drama queen.