I have a guest that is wanting to stay in July, but cannot pay the entire fee at one time. She has asked it she could pay a deposit to hold the booking, and then pay the rest in April. Is there a way to do this?
No, there is no way to pay a deposit and then the full amount at a later date.
You could ask the guest to book the first week and pay for that, and then agree to block off the remaining 3 weeks until they have the money. The will be charged a second set of fees and you run the risk that the booking will not materialise.