Wife had stroke, Husband seeks legal authority to manage finances
First, we must discuss "incapacity" as it relates to your wife's loss of brain function and her current mental and physical condition following her recent stroke.
If the incapacity you mention has made her mentally incompetent (a legal, not a medical concept), then she lacks capacity to execute a power of attorney and any power she signed could be void or voidable. In that event and to manage her financial affairs, you would need to initiate a legal proceeding known as a conservatorship proceeding in which you would allege that she is financially incapable and nominated yourself as conservator. As a general rule, courts are reluctant to appoint co-fiduciaries, co-conservators.
If, however, your wife's loss of brain function has not diminished her cognative ablilities, but instead and for example, has diminished her power of speech or her mobility, then she could execute a power of attorney, assuming she can make her signature or her mark. I have included a link below to US Legal Forms website for a Texas durable power of attorney form that is effective immediately upon execution.
You may decide you desire or need the assistance of an experienced Texas lawyer in this matter. I have include a link to US Legal's lawyer referral webpage below.