For some reason she just want ready to ovulate. There are a lot of factors that can induce a successful breeding: timing, cooling, photoperiod, overall health prior to breeding, fertility of the male, breeding history of the female etc... Some people get successful breedings and don't pay attention to any of the forementioned factors and some experienced breeders "do everything right" and still don't get some animals to breed. It's never easy to just say, "fix this and all will work better next year." Some females just dont get the trigger that they need. I had several females this year that bred like rabbits and for whatever reason, never ovulated. ...and they were kept under the same conditions that several other females did ovulate. Sometimes, I'm looking at several big females and left scratching my head and thinking, "You really should have gone this year...." Some of my most mature females did not ovulate this year, while some of my younger females that were just bumping 9'-10' bred successfully. Don't fret if your female didn't ovulate...it's just not always that simple.
All that being said...I don't have enough info to help you diagnose this particular situation. If you can provide dates of cooling, temps, hot spot temp, night drops etc... Many folks on this forum can help you further. Everyone has their own style and can find success through different methods. There is no one right method for breeding success.
Here's my recipe, and those that know me, know that I usually use the holidays as three of my big milestones:
Halloween - stop feeding
Thanksgiving - start cooling and reduce photoperiod. Gradually reduce temps over the next 3-4 weeks to 84 degree high, 78 degree night. hot spot 87 day - 84 night. At the same time, reducing down to 8 hours of light. When the females are ready, they'll stay away from the hot spot.
Christmas - introduce pairs
January is usually when most activity occurs. I start to bring up the temps and photo period around the middle / end of January. -begin feeding small meals.
February: breeding continues and ovulations occur.
March - April: eggs deposited.
May - June: eggs hatch...up to this point, the animals have been doing all the work. Now your work really begins!!
This is a great hobby...limit your numbers, do it for the love of the animals and you will never tire or burn out. Enjoy.
Keep your eyes on the half dwarf burms. Those animals are amazing and require their own discussion. 
Tom