You can hire anyone that you want to. This includes family members also. You must have record of payment in order to count it as a deductable medical expense with the VA. I can send you a copy of the VA regulation on this if you want.
You may also want to consider downloading a copy of the new POA form and have your mother sign to appoint you as her representative. This will allow you to present paperwork to the VA on her behalf and also to obtain status reports on her case. You can also request a complete copy of her claim's file if you need it.
As I recall, you had already made an application, so the effective date should remain the same. Keep in mind that a veteran and/or widow can be entitle to aid & attendance even if they are staying at home. The key is, 'the need of assistance'. From your posting, I would say your mother would be entitle to the aid & attendance benefit. Apply for that and if she is not entitle, the VA will consider the same claim for the housebound rating.
I hope this information is of help to you. Let me know if you have any additional questions.