How to get older child to swallow pills?

My step daughter will be 12 in April. She still struggles with swallowing pills. I honestly can’t remember when I started being able to, but her brother has been able to for years now and he’s 13. She weighs about 110 and I don’t think children’s medicine is really effective on her now, but it’s a disaster getting her to try and swallow one! I tried getting her to swallow half a Benadryl last summer when she had allergies and she nearly threw up and started crying. I just know eventually she’s going to have to. They both get bad allergies and giving her a Zyrtec or Benadryl would help so much if she were able to. It would also be nice to stop buying children’s medicine and having us all use the same things lol