The only way is if she is also charged with kidnapping, also.
The obstacle the prosecutors will face is her intent. The defense will argue that she didn't intend to hit him, she didn't do anything to restrain him, and she didn't intend for him to die. She wanted the whole problem to just go away. He'll argue that she was merely negligent in not getting aid for the victim.
I think it's a stretch to add a kidnapping charge, but the prosecution can certainly make that attempt. A prosecution for capital murder doesn't preclude the jury from finding her guilty of a lesser charge.
Sec. 19.03. CAPITAL MURDER. (a) A person commits an offense if he commits murder as defined under Section 19.02(b)(1) and:
~ ~ (1) the person murders a peace officer or fireman who is acting in the lawful discharge of an official duty and who the person knows is a peace officer or fireman;
~ ~ (2) the person intentionally commits the murder in the course of committing or attempting to commit kidnapping, burglary, robbery, aggravated sexual assault, arson, or obstruction or retaliation;
~ ~ (3) the person commits the murder for remuneration or the promise of remuneration or employs another to commit the murder for remuneration or the promise of remuneration;
~ ~ (4) the person commits the murder while escaping or attempting to escape from a penal institution;
~ ~ (5) the person, while incarcerated in a penal institution, murders another:
~ ~ ~ (A) who is employed in the operation of the penal institution; or
~ ~ ~ (B) with the intent to establish, maintain, or participate in a combination or in the profits of a combination;
~ ~ (6) the person:
~ ~ ~ (A) while incarcerated for an offense under this section or Section 19.02, murders another; or
~ ~ ~ (B) while serving a sentence of life imprisonment or a term of 99 years for an offense under Section 20.04, 22.021, or 29.03, murders another;
~ ~ (7) the person murders more than one person:
~ ~ ~ (A) during the same criminal transaction; or
~ ~ ~ (B) during different criminal transactions but the murders are committed pursuant to the same scheme or course of conduct; or
~ ~ (8) the person murders an individual under six years of age.
~ (b) An offense under this section is a capital felony.
~ (c) If the jury or, when authorized by law, the judge does not find beyond a reasonable doubt that the defendant is guilty of an offense under this section, he may be convicted of murder or of any other lesser included offense.