I'm not one to normally say you need to ditch your girlfriend but this to me raises so major ref flags. If she is accusing you of cheating and trying to use this as proof then there is no trust in the relationship from her end. If you two have been together a long time and you think it's worth saving then I would suggest some counseling to work in her trust issues.

pretty risky cheating on her with her mother. well go big or go home is what they say

ask her to call her mother and see if it was her who sent the flowers

I have to say that this is not okay. This is not normal behavior. She might need professional help.

I think it's kind of weird that you said it's ALSO her mothers name.

Let her mom know what's happening. sometimes a little bit of shame talk from a mom is enough to make someone see the light

That's a very clever move to get a side chick with the same name as your girlfriend's mom. Rookie mistake to tell her your address!

I can see why she is upset though. The flowers should have been wrote out to her and op. Another thing Venessa is a very popular name and most parents will refer to themselfs as mom or dad to their child's significant other. Or they might even adress themselfs with their last name. It's a FML for you because her mom caused so much grief but it is an FML for her as well.

???OMG. Did she realize her rather gigantic error. Or did she get stubborn and insist you are lying.

Sorry op, try telling your girlfriend to call her mom.