Sorry to hear of the issue.
As a tenant you have a right to quiet enjoyment of the property. Even if the tenancy agreement doesn't mention this, it is an implied term of a tenancy meaning it applies automatically.
She cannot turn up unannounced and can only attend if there are works required, and only if reasonable notice is given.
It sounds like she is harassing you - you can reasonably refuse any further request for her to enter the property and an injunction from the local county court could be applied for. You may also be able to claim compensation for harassment.
You can word it yourself or you can use a lawyer - I would go with a lawyer as they may offer you no win no fee terms meaning you pay nothing up front. If they recover damages then they could charge a success fee.
Here are a few choices for you if you would like to use a lawyer :
1. Knights Law, tel: 01204 655614, email:***@******.***
2. Stephensons Solicitors, tel: 0161(###) ###-####
3. Duncan Lewis, tel: 0333(###) ###-####