It will only get slightly larger than it is now, and the mother is long-gone. What's so horrible about a little harmless Garter Snake being on the property?,....it will cause absolutely ZERO harm to anyone,or anything..C'mon!
I assume you let birds fly in and out of your property,..right?,...it's the same exact thing. It's just another harmless animal that wants to just be allowed to survive, that's all. It won't "attack" anyone, and the only reason to fear it is all in the mind, nothing more, nothing less.
If you go on about your everyday life without worrying about it, it will certainly do the same. It's just like a frog, or a bird, or a chipmunk in your yard....no big deal at all.
best regards, ~Doug
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"Better to be silent and thought a fool, than to open mouth and remove any doubt!"