Potty training accidents

My 3 year old is fully potty trained. She typically goes weeks with no accidents. Now all of the sudden lately she’s having anywhere from 1-3 accidents a day. She knows how to go to the potty whenever she needs to go, she wipes herself, and does it completely on her own. since the accidents started I tell her to go try the potty every 15 or so min just like when we first started potty training. However; the accidents just aren’t stopping. And the part that really bothers me is she won’t tell me. She’ll pee in her underwear and just sit it in and continue playing. When I ask her about it she just says “it’s an accident” “I had another accident” etc. she really just doesn’t seem to care. I don’t feel like this is an issue to yell at, as obviously accidents happen. But I don’t know how to tackle this issue. Any advice is much appreciated ❤️