when would be the best time to tell my gran im getting a puppy?

i am going to be getting a puppy probably next year at easter but possibly sooner.

thing is i am really close to my gran and i tell her everything but i know if i tell her im getting a puppy she will worry.

she has a lot to worry about what with me being severely disabled and ill, her not being able to get in touch with my uncle (her youngest sun), her daughter (m aunt) over doing things and never giving her self a rest even though she has hyperthyroidism and never seems to have a day off, her best friend struggling to get hearing aids that work, her other friend (a man) being very clingy and weird (he came and looked through her window i one evening with his face up to the glass and he even called her in the middle of the nigh (she has a phone by her bed) and staying silent. when he eventually spoke he denied that he even called her and infact that she called him but it was not her number, she could not get back to sleep after that as she lives alone. he also randomly comes over and goes into her garden. he tries to get her to tell him personal things.

we don't think we should tell her at least until the puppy is born but we also think i should wait until i have the puppy or am on my way to get it but i am thinking about not telling her at all and she just finds out when she sees the puppy in person.

i just don't want her to needlessly worry.