Your aunt can apply in family visitor category if close relative otherwise general visitor. Application form VAF1A.
She must make it clear on the visa application form that she intends to leave UK at end of her stay (1 mth)and in any case before visa expiry. She should not stay beyond what is declared or it could affect future visa applications.
She needs to declare her relationship with you. You need to send sponsorship declaration/letter in support of her application with undertakings as to maintenance and accomodation.
Check entry clearance guidance for visitors at:
Check guidance on maintenance and accomodation requirement:
Part 11 of the visa application form suggests supporting documentation but is not an exhaustive list. Rule of thumb: show as much relevant evidence as possible. Do not give immigration officer a chance to object.
Its important to get it right on this occasion. There are generally limited rights of appeal for general visitors if visa application refused. If you are a niece within family visitor regulations definition then appeal rights can be engaged.
An adverse immigration record must be avoided or any future settlement application could be prejudiced (even though strictly speaking previous refusals are not meant to prejudice future applications). Visa refusals make it difficult to travel abroad especially Western countries.
Hope that helps.
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