The dual Olympic champion cyclist was riding the nine-year-old Pacha Du Polder for a second time, with the pair having been beaten in a photo-finish at Milborne St Andrew point-to-point in late January.
The Paul Nicholls-trained gelding was the 8-13 favourite for this three-mile contest and Pendleton gave her mount time to find his feet, initially dropping him out at the rear of the six-runner field.
Pacha Du Polder gradually warmed to his task and was moving closer to the leaders when he was slightly impeded by Baltic Blue at the seventh fence.
Pendleton and Baltic Blue’s rider Carey Williamson crashed to the ground, but both riders were soon on their feet.
Pacha Du Polder, who carries the colours of leading owners the Stewart family and finished second over the Grand National fences in the Fox Hunters’ Chase at Aintree last term, had already been earmarked as Pendleton’s intended Festival ride in the St James’s Place Foxhunter Chase on March 18.
Pendleton said: “I was really looking forward to the race and another opportunity to ride such a fabulous horse.
“Pacha Du Polder is so excellent and I’ve thoroughly enjoyed every fence we’ve schooled over.
“I’m very disappointed I didn’t given him a fair shot. He was an odds-on favourite and it was a disappointing job from me, I think.
“I think the horse next to me (Baltic Blue) propped in and as we both came over together he sort of knocked me to one side.
“I didn’t have four feet on the ground and I came out the side door.
“It’s one of those things, it’s racing - it’s what happens.
“It doesn’t always go to plan and it’s onwards and upwards.”
Pendleton, 35, said she has escaped injury and that she still wants to ride Pacha Du Polder at the Cheltenham Festival.
She said: “I hope Cheltenham is still the plan.
“Hopefully I’ll get another opportunity to sit on him, and get as many rides in as possible between now and then.
“It’s up to the team of experts to decide whether I’m ready for Cheltenham - I hope I am.
“I appreciate this is what happens, and it was going to happen sooner or later.
“I’ve had a good run, I’ve not had a fall until now really.