My question involves landlord-tenant law in the State of: Washington

When I moved into a house with my ex roommate she said she was broke and couldn't afford the deposit. I paid the first month's rent and deposit up front, and the landlord wrote the receipt for the deposit in my name (not both). After we moved out the landlord returned the deposit directly to me since I was the one who paid it.

Now she's claiming that she paid me back in cash for the deposit and sent me a nasty email threatening to to sue both me and the landlord if I don't send her money via Pay Pal within a week. She claims the landlord illegally sent the refund to just me, and that she's entitled to half because her name was on the lease. She did pay me back in cash for the first months rent, but gave me nothing but excuses for the deposit and promises that she'd pay for any damages.

She says if I don't pay half the refund she'll sue me for the refund plus an additional $75 for the last months internet, gas, and power bill which were in her name. However I had to pay her past due utility bill (plus late fees) and all of the damages taken our of the deposit were in her section of the house, totaling $350. In additions to trashing the house she also refused to help with any of the clean up.

I'm assuming the $350 is lost, even though I didn't make the damages, but can she really sue us?