It looks like you're the one dating a materialistic girlfriend and not you friend. So you should man up and stop saying my friend's girlfriend.

Ladies want to be loved, cared for and pampered with gifts especially on an important day like the Valentine's day. However, just as all shoes have different sizes, that's how we all have different financial capacities. If a lady cannot accept or is not satisfied with the gifts and money I can shower her at my level. Then, It's a red flag for me and I'd gladly pack my bag and baggages and run a way, because I'll not steal to impress a lady.