Honestly, get names of all the barns she’s boarded at and check references. Maybe she’s just socially awkward or nervous about having to move her horses.
Its not realistic to modify for fences for one boarder. If there is room for her to put up her own paddock, maybe let her.
Your prices are your prices. Lots of barns around me have multi horse deals or discounts if your horse can be used x number of hours in their lessons programs etc. Only you know if you can afford that.
I boarded at a crazy magnet net barn for five years. The barn owner was a true horse trader and went through two crazy wives during my time there.
There was a boarder with a horse severely injured there. Lawsuit went nowhere because of the unpredictable nature of horses. BO had a well worded, signed contract.
I understand needing money. I was a single mom with a dead beat ex that didn’t help out. Any job you have, where you deal with the public you have some that are easy and others that aren’t. I never had the luxury of deciding how much I would put up with because if there was no income, there was no mortgage payment, car payment or groceries.
If her references check out, write the contract for the exact length of time she needs only, she releases you from liability, you may terminate the contract at any time, she must give 30 days and have a zero balance before she can remove horses. Protect yourself legally and take her money. You can put up with anything for six months if you really need income.