Looks to me like (after watching the Daily Fail clip) that the woman on the horse has lost her temper / is acting the billy big ********s and is attempting to intimidate the protesters by threatening them with running them down.
The fella that grabs the horse is also out of order, but probably acting in panic / self defence. The woman then assaults him further with a riding crop.
That's dangerous and common assault. She's lucky she didn't injure him more badly or she would in all probability and quite rightly, get locked up for ABH.
The trespass is irrelevant. You can't just decide to forcibly eject someone from your (is it even hers?) property without exceptional circumstances and with moderate force. Certainly not from a field, whilst riding a horse... That's totally excessive. If she's trying to do so, which it looks like she is, she should definitely be charged with common assault at least.