Very good question Darlene, I would like to know too.
This has happened to me a lot and here are some tips I've learned a long the way to keep the bristles in shape for as long as possible (for acrylics or watercolors - oils may be different):
Hope this helps! If anyone else has tips to share, please do! I tend to buy cheap brushes so when the bristles start to flare out I just buy a new one. :)