I think MRI is the most important and appropriate test in this clinical scenario. Similarly MR Angiography is also essential and helps in risk assessing the risk of similar episodes in the future. Other tests which are mentioned are appropriate too. I disagree with the doctors who believe that this was not required.

Any MRI done at the time of TIA will most likely be normal...TIA is the initial warning for a future stroke. If her BP remains uncontrolled, and she continues to have repeated TIAs, or symptoms as you have described, it is very likely she has developed/developing another stroke event....I presume she is already on blood thinners and lipid lowering drugs after her TIA...In my opinion, with the current scenario, she needs to be seen by a neurologist and definitely requires a repeat MRI Brain with MRA, also Doppler study of her neck vessels and a cardiology opinion.