Answer:
Dear [Mother's friend's name],
Thank you so much for your kind offer to have me live with you after your return from abroad. I truly appreciate your generosity and thoughtfulness. However, I regret that I am unable to accept your offer at this time for the following reasons:
Family Obligations: I have responsibilities and obligations to my family that make it difficult for me to leave my current living arrangements.
Work or School Commitments: I have work or school commitments that require me to stay in my current location.
Personal Reasons: There are personal reasons that make it necessary for me to remain where I am currently living.
Again, I thank you for your offer and apologize for any inconvenience this may have caused. I look forward to seeing you soon and catching up on your travels.
Sincerely,
[Your name]