Each Apple device is linked/associated with an Apple ID of the person who did the setup.
Activation Lock prevents anyone who is not the owner from using this iPad.
To unlock the Pad, you need the Apple ID and password of the previous owner, that were used during set up.
So you have to contact the previous owner.
The your aunt has to read -> this Apple article: What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch -> What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support
Then she has to remove the iPad from her account, see this Apple article:
Check your Apple ID device list to see where you're signed in
Check your Apple ID device list to find where you're signed in - Apple Support
Then you can sign in with your own Apple ID.
See the following Apple articles:
Activation Lock for iPhone, iPad, and iPod touch
Activation Lock for iPhone, iPad, and iPod touch - Apple Support
How to remove Activation Lock -> How to remove Activation Lock – Apple Support (UK)
Read this before you use a 2nd hand iPad.
You can also contact Apple support for help, -> Get Support (apple.com)
You have to show proof of ownership of your product, provide all documentation showing your purchase of the device.
If you do not have additional proof of ownership, contact the reseller. They may be able to provide the original purchase document.
Once Apple receive your proof of ownership, Apple will further review your request and provide an update.
See also -> Keep your receipt after you buy an Apple device
Keep your receipt after you buy an Apple device – Apple Support (UK)
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she can't remember the password for her email nor can she remember the password of the apple ID,
Ask If your aunt to read ⤵️
See -> If you can't connect or sign in to iCloud
If you can't connect or sign in to iCloud - Apple Support
Have you forgotten your Apple ID?, Check your Apple ID via your email box, see this Apple article: If you forgot your Apple ID
If you forgot your Apple ID email address or phone number - Apple Support
OR see -> Having trouble signing in?
https://iforgot.apple.com/password/verify/appleid
Have you forgotten your Apple ID password? -> See this Apple article: If you forgot your Apple ID password
If you forgot your Apple ID password - Apple Support
Then see this Apple article: What to do after you change your Apple ID or password
What to do after you change your Apple ID or password - Apple Support