She is citizen of India and an MP for the elected term. What more you want?
According to law, she can become a PM as well in future, if her party gets majority or forms a govt by coalition and the MPs of the coalition elect her as PM..
That she is given a UPA chairperson status and treated like a cabinet minister by the parties in power and that she remains a PM by proxy are all aberrations of politics outside the constitutional purview..
The argument that she would not be eligible to become a PM was rubbished already by many experts.. She deliberately gave up the claim to become PM when the party was ready to crown her with the coveted post just to earn the sympathy of people and to appear as not hankering for power...
Her actual ability to hold the post are not known to us, but the sycophants of the congress known for loyalty to Nehru family are eager to make her the PM regardless of her worth for the highly sensitive post calling for much political sagacity..
As for commoner like me, the fact that the govt (under her obvious direction) glaringly influences CBI to let off the Italian businessman wanted in Bofors case, casts a shadow about her ethical merits also to hold the high post..!
The choice of a party woman with no special social contribution or fame, as Rashtrapathi - in spite of many doubts raised on the candidate's background in the media - just on the only basis of her loyalty to the party chief, casts further taint on the shadow PM...
But these are beside the point.. Your question is already answered in para.1 The supplemental info is on a guess that you are doubting her extra constitutional influences.. yes, they are extra constitutional but she is the UPA chair person and principal party's President, who can influence their PM appointee Dr M to do as she desires.. For this no big constitutional position is required..!!
We saw how Mrs Indira in spite of her great lineage (of freedom fighters) brought discredit to the national party by declaring emergency on dubious grounds.. We dont know what this lateral entrant to the lineage would do for the party and the nation..?!
God help us!