What is the meaning of the line "For only Gossamer, my Gown" in "Because I Could Not Stop for Death—"?

In this poem, Dickinson describes death. When a person dies—goes on what the speaker compares to a polite carriage journey to the grave—the body gradually gets colder and colder. As the speaker in this poem approaches her own grave—described in the poem as an underground house—she grows chilled. In the poem, this is explained as being out as the sun sets, a time when the temperature drops and it gets chillier. She is described as wearing clothes made of the thinnest of fabrics. Gossamer is a very light cloth, and tulle is a thin, netted material. The speaker is getting chilled because of the very light clothing she is wearing; this becomes a metaphor for the cold and chill quality of a corpse.
The speaker's lightweight clothing might also indicate she was not prepared for death. This is supported by the fact its arrival seems to have taken her by surprise. She notes, for instance, that because she couldn't (wasn't ready to) stop for death, it stopped for her. During the journey, she doesn't seem to know where she is headed. As we can see, Dickinson uses stock images to describe death, such as coldness and sunset, but she uses them in fresh and startling ways. Being chilled from wearing gossamer and tulle is one of the fresh images she uses.

This morbid poem by Emily Dickinson describes her journey with Death—i.e. her passage from this life to the next one.
Before this particular line mentioning gossamer, we read:

“We passed the setting Sun –
Or rather – He passed us –
The Dews grew quivering and chill –
For only Gossamer, my Gown –
My Tippet, only Tulle”
(Poets.org).

When Dickinson mentions the sun passing her and Death, she describes how it grows chilly ("The Dews grew quivering and chill"). She then emphasizes how thin her clothing is, saying that her gown is made of gossamer. Gossamer is used to describe something extremely thin, filmy, and airy, like spider web. The meaning can be further seen as she goes on to say that her tippet (a scarf-like accessory) is only tulle. Tulle is the fabric many ballet skirts are made of. It is a very fine netting with many tiny holes. 
Gossamer and tulle are both extremely thin fabrics, and by themselves would make you feel almost as if you were wearing nothing at all. Here Dickinson is emphasizing the chilly, cold nature of death, and saying that her clothing feels insufficient for its dark temperature.
https://poets.org/poem/because-i-could-not-stop-death-479

https://www.dictionary.com/browse/tippet