My First Offer

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I'm a real estate newbie.
I mailed my first offer to an out of town seller (without a deposit).
I sent an Option Contract for Sale/Purchase.
Owner asking $159K for a beautifully renovated 2 Br, 1 Ba., Screened
Patio/Pool house in a nice community with homes ranging from
$100K to $400K.
Comps in Zillow showed homes with 2Br/1Ba sold from $115K to $175K.
I offered $139,900 which is 88% of the asking price.
My exit strategy is to wholesale it.
I visited the house, it's great and free and clear.
It's worth the retail price.

In summary;
Retail Price - $159K
ARV - $159K
Repairs - $ 0
Bal. owed - $ 0

The seller called me today to say she will counter my
offer because it was low. I said ok, send me your counter offer.
My question(s) is:
How should I have structured my offer to AVOID a counter offer and
how should I respond to the seller's counter offer if it cuts into my
projected profit?

Thanks,
H C