No. You would be looking at FLR fp which has a long wait time and frequently refused.
If there are medical grounds, then how did she get to the UK in the first place?? If she has a refused spouse visa on her record, it is unlikely she will be granted a visitor visa due to her intention to settled being known. Ho is very aware if migrants trying to get in with a visitor visa and then change to a spouse or family visa, the abuse of this route has made it so much harder for everyone.
I suggest you do the visa process properly and not try to find loop holes you think exist as it will end up costing you a lot of money and she will have Jo free NHS use and you will have to pay 150% of the cost etc.