You could try putting a low-flow nipple on the bottle, so that it takes more effort to drink it. That should slow down most babies. (The truth is that landing is more likely to cause ear problems than takeoff, and the pressure change starts happening as soon as the descent begins, so it can take rather a while.)
If you are really worried that the usual solutions won't work, you could ask your Ped. for a prescription for Auralgan or the generic equivalent. Auralgan is an analgesic eardrop; it will stop any ear pain very quickly if it happens.
Getting a scrip for it is rather difficult, because if it is over-used, you could mask the symptoms of a condition that needs medical attention, such as an ear infection. You would need to assure the ped. that you ONLY intend to use it if it becomes necessary during the flight, one time in the flight, and that you will get medical attention for her ASAP if she shows signs of ear pain after you have landed. (It's not that the drug itself is dangerous, it's just that Dr's don't want a child to end up with hearing loss from an untreated infection. The drops contain antipyrine and benzocaine.)
I have a scrip for Auralgan myself, as I get chronic ear infections. I don't use it on the kids except in emergencies. To show you how rare it is for a ped. in the US to prescribe it, a couple of weeks ago DS got an earache at bedtime, and I used the Auralgan so that we could all sleep until I could get him to the ped in the morning. When I told the nurse what I had given him, she didn't know what it was. (Interestingly, Auralgan is available OTC in Canada, where they approach the treatment of ear infections a bit differently than US peds. do.)