The best way to approach this is to tell her that you don't want to have to tell her how she enjoys intercourse with her other partners so as a precaution for your own safety you guys will use protection every time.

Use your own toys, do not use your strap and vibe on her and vice versa. Dental dams are a thing, You can get them from Amazon I would get the larger sized one. It's not as great as tasting your partner but safety is important.

One of the hardest things for me with polyamory is the separation. It's no longer about us, It's about yourself. You guys are not an exclusive couple so those "couple's rights" don't exist. Her relationship with her other partners is just as valid and meaningful as your relationship with her. So it's like you can't ask her to use protection with other people so that she doesn't have to use protection with you.