Suppose a lady who normally Davens (prays) Mincha missed Mincha one day. Now this lady never Davens Maariv. Must she Daven Maariv to do Tashlumin or can she just Daven one Shemona Esrei for the missed Mincha?
Tashlumin always has to be after an ordinary obligatory prayer, so in your case in order to say the Tashlumin she would have to Daven Maariv first and then say the Tashlumin. (Halichot Shelomo Tefillah chapter 13 footnote יא)
While the above is I believe the more commonly held position, I note that Rabbi Dr. Nahum Rabinovitch rules (Siach Nachum OC 10) [in the context of Friday night, but seemingly applicable at other times] that if a woman is stuck and can't follow the above recommendation, she can pray just once as Tashlumin and intend that if this can't be a Tashlumin it should be a Nedava (voluntary) prayer.